/*

 * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos

 *

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 *  * Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

 *

 *  * Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 *

 *  * Neither the name of JSR-310 nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

package java.time;

import static java.time.LocalTime.NANOS_PER_SECOND;

import static java.time.LocalTime.SECONDS_PER_DAY;

import static java.time.LocalTime.SECONDS_PER_HOUR;

import static java.time.LocalTime.SECONDS_PER_MINUTE;

import static java.time.temporal.ChronoField.INSTANT_SECONDS;

import static java.time.temporal.ChronoField.MICRO_OF_SECOND;

import static java.time.temporal.ChronoField.MILLI_OF_SECOND;

import static java.time.temporal.ChronoField.NANO_OF_SECOND;

import static java.time.temporal.ChronoUnit.DAYS;

import static java.time.temporal.ChronoUnit.NANOS;

import java.io.DataInput;

import java.io.DataOutput;

import java.io.IOException;

import java.io.InvalidObjectException;

import java.io.ObjectInputStream;

import java.io.Serializable;

import java.time.format.DateTimeFormatter;

import java.time.format.DateTimeParseException;

import java.time.temporal.ChronoField;

import java.time.temporal.ChronoUnit;

import java.time.temporal.Temporal;

import java.time.temporal.TemporalAccessor;

import java.time.temporal.TemporalAdjuster;

import java.time.temporal.TemporalAmount;

import java.time.temporal.TemporalField;

import java.time.temporal.TemporalQueries;

import java.time.temporal.TemporalQuery;

import java.time.temporal.TemporalUnit;

import java.time.temporal.UnsupportedTemporalTypeException;

import java.time.temporal.ValueRange;

import java.util.Objects;

/**

 * An instantaneous point on the time-line.

 * <p>

 * This class models a single instantaneous point on the time-line.

 * This might be used to record event time-stamps in the application.

 * <p>

 * The range of an instant requires the storage of a number larger than a {@code long}.

 * To achieve this, the class stores a {@code long} representing epoch-seconds and an

 * {@code int} representing nanosecond-of-second, which will always be between 0 and 999,999,999.

 * The epoch-seconds are measured from the standard Java epoch of {@code 1970-01-01T00:00:00Z}

 * where instants after the epoch have positive values, and earlier instants have negative values.

 * For both the epoch-second and nanosecond parts, a larger value is always later on the time-line

 * than a smaller value.

 *

 * <h3>Time-scale</h3>

 * <p>

 * The length of the solar day is the standard way that humans measure time.

 * This has traditionally been subdivided into 24 hours of 60 minutes of 60 seconds,

 * forming a 86400 second day.

 * <p>

 * Modern timekeeping is based on atomic clocks which precisely define an SI second

 * relative to the transitions of a Caesium atom. The length of an SI second was defined

 * to be very close to the 86400th fraction of a day.

 * <p>

 * Unfortunately, as the Earth rotates the length of the day varies.

 * In addition, over time the average length of the day is getting longer as the Earth slows.

 * As a result, the length of a solar day in 2012 is slightly longer than 86400 SI seconds.

 * The actual length of any given day and the amount by which the Earth is slowing

 * are not predictable and can only be determined by measurement.

 * The UT1 time-scale captures the accurate length of day, but is only available some

 * time after the day has completed.

 * <p>

 * The UTC time-scale is a standard approach to bundle up all the additional fractions

 * of a second from UT1 into whole seconds, known as <i>leap-seconds</i>.

 * A leap-second may be added or removed depending on the Earth's rotational changes.

 * As such, UTC permits a day to have 86399 SI seconds or 86401 SI seconds where

 * necessary in order to keep the day aligned with the Sun.

 * <p>

 * The modern UTC time-scale was introduced in 1972, introducing the concept of whole leap-seconds.

 * Between 1958 and 1972, the definition of UTC was complex, with minor sub-second leaps and

 * alterations to the length of the notional second. As of 2012, discussions are underway

 * to change the definition of UTC again, with the potential to remove leap seconds or

 * introduce other changes.

 * <p>

 * Given the complexity of accurate timekeeping described above, this Java API defines

 * its own time-scale, the <i>Java Time-Scale</i>.

 * <p>

 * The Java Time-Scale divides each calendar day into exactly 86400

 * subdivisions, known as seconds.  These seconds may differ from the

 * SI second.  It closely matches the de facto international civil time

 * scale, the definition of which changes from time to time.

 * <p>

 * The Java Time-Scale has slightly different definitions for different

 * segments of the time-line, each based on the consensus international

 * time scale that is used as the basis for civil time. Whenever the

 * internationally-agreed time scale is modified or replaced, a new

 * segment of the Java Time-Scale must be defined for it.  Each segment

 * must meet these requirements:

 * <ul>

 * <li>the Java Time-Scale shall closely match the underlying international

 *  civil time scale;</li>

 * <li>the Java Time-Scale shall exactly match the international civil

 *  time scale at noon each day;</li>

 * <li>the Java Time-Scale shall have a precisely-defined relationship to

 *  the international civil time scale.</li>

 * </ul>

 * There are currently, as of 2013, two segments in the Java time-scale.

 * <p>

 * For the segment from 1972-11-03 (exact boundary discussed below) until

 * further notice, the consensus international time scale is UTC (with

 * leap seconds).  In this segment, the Java Time-Scale is identical to

 * <a href="http://www.cl.cam.ac.uk/~mgk25/time/utc-sls/">UTC-SLS</a>.

 * This is identical to UTC on days that do not have a leap second.

 * On days that do have a leap second, the leap second is spread equally

 * over the last 1000 seconds of the day, maintaining the appearance of

 * exactly 86400 seconds per day.

 * <p>

 * For the segment prior to 1972-11-03, extending back arbitrarily far,

 * the consensus international time scale is defined to be UT1, applied

 * proleptically, which is equivalent to the (mean) solar time on the

 * prime meridian (Greenwich). In this segment, the Java Time-Scale is

 * identical to the consensus international time scale. The exact

 * boundary between the two segments is the instant where UT1 = UTC

 * between 1972-11-03T00:00 and 1972-11-04T12:00.

 * <p>

 * Implementations of the Java time-scale using the JSR-310 API are not

 * required to provide any clock that is sub-second accurate, or that

 * progresses monotonically or smoothly. Implementations are therefore

 * not required to actually perform the UTC-SLS slew or to otherwise be

 * aware of leap seconds. JSR-310 does, however, require that

 * implementations must document the approach they use when defining a

 * clock representing the current instant.

 * See {@link Clock} for details on the available clocks.

 * <p>

 * The Java time-scale is used for all date-time classes.

 * This includes {@code Instant}, {@code LocalDate}, {@code LocalTime}, {@code OffsetDateTime},

 * {@code ZonedDateTime} and {@code Duration}.

 *

 * <p>

 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>

 * class; use of identity-sensitive operations (including reference equality

 * ({@code ==}), identity hash code, or synchronization) on instances of

 * {@code Instant} may have unpredictable results and should be avoided.

 * The {@code equals} method should be used for comparisons.

 *

 * @implSpec

 * This class is immutable and thread-safe.

 *

 * @since 1.8

 */

public final class Instant

        implements Temporal, TemporalAdjuster, Comparable<Instant>, Serializable {

    /**

     * Constant for the 1970-01-01T00:00:00Z epoch instant.

     */

    public static final Instant EPOCH = new Instant(0, 0);

    /**

     * The minimum supported epoch second.

     */

    private static final long MIN_SECOND = -31557014167219200L;

    /**

     * The maximum supported epoch second.

     */

    private static final long MAX_SECOND = 31556889864403199L;

    /**

     * The minimum supported {@code Instant}, '-1000000000-01-01T00:00Z'.

     * This could be used by an application as a "far past" instant.

     * <p>

     * This is one year earlier than the minimum {@code LocalDateTime}.

     * This provides sufficient values to handle the range of {@code ZoneOffset}

     * which affect the instant in addition to the local date-time.

     * The value is also chosen such that the value of the year fits in

     * an {@code int}.

     */

    public static final Instant MIN = Instant.ofEpochSecond(MIN_SECOND, 0);

    /**

     * The maximum supported {@code Instant}, '1000000000-12-31T23:59:59.999999999Z'.

     * This could be used by an application as a "far future" instant.

     * <p>

     * This is one year later than the maximum {@code LocalDateTime}.

     * This provides sufficient values to handle the range of {@code ZoneOffset}

     * which affect the instant in addition to the local date-time.

     * The value is also chosen such that the value of the year fits in

     * an {@code int}.

     */

    public static final Instant MAX = Instant.ofEpochSecond(MAX_SECOND, 999_999_999);

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = -665713676816604388L;

    /**

     * The number of seconds from the epoch of 1970-01-01T00:00:00Z.

     */

    private final long seconds;

    /**

     * The number of nanoseconds, later along the time-line, from the seconds field.

     * This is always positive, and never exceeds 999,999,999.

     */

    private final int nanos;

    //-----------------------------------------------------------------------

    /**

     * Obtains the current instant from the system clock.

     * <p>

     * This will query the {@link Clock#systemUTC() system UTC clock} to

     * obtain the current instant.

     * <p>

     * Using this method will prevent the ability to use an alternate time-source for

     * testing because the clock is effectively hard-coded.

     *

     * @return the current instant using the system clock, not null

     */

    public static Instant now() {

        return Clock.systemUTC().instant();

    }

    /**

     * Obtains the current instant from the specified clock.

     * <p>

     * This will query the specified clock to obtain the current time.

     * <p>

     * Using this method allows the use of an alternate clock for testing.

     * The alternate clock may be introduced using {@link Clock dependency injection}.

     *

     * @param clock  the clock to use, not null

     * @return the current instant, not null

     */

    public static Instant now(Clock clock) {

        Objects.requireNonNull(clock, "clock");

        return clock.instant();

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Instant} using seconds from the

     * epoch of 1970-01-01T00:00:00Z.

     * <p>

     * The nanosecond field is set to zero.

     *

     * @param epochSecond  the number of seconds from 1970-01-01T00:00:00Z

     * @return an instant, not null

     * @throws DateTimeException if the instant exceeds the maximum or minimum instant

     */

    public static Instant ofEpochSecond(long epochSecond) {

        return create(epochSecond, 0);

    }

    /**

     * Obtains an instance of {@code Instant} using seconds from the

     * epoch of 1970-01-01T00:00:00Z and nanosecond fraction of second.

     * <p>

     * This method allows an arbitrary number of nanoseconds to be passed in.

     * The factory will alter the values of the second and nanosecond in order

     * to ensure that the stored nanosecond is in the range 0 to 999,999,999.

     * For example, the following will result in exactly the same instant:

     * <pre>

     *  Instant.ofEpochSecond(3, 1);

     *  Instant.ofEpochSecond(4, -999_999_999);

     *  Instant.ofEpochSecond(2, 1000_000_001);

     * </pre>

     *

     * @param epochSecond  the number of seconds from 1970-01-01T00:00:00Z

     * @param nanoAdjustment  the nanosecond adjustment to the number of seconds, positive or negative

     * @return an instant, not null

     * @throws DateTimeException if the instant exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public static Instant ofEpochSecond(long epochSecond, long nanoAdjustment) {

        long secs = Math.addExact(epochSecond, Math.floorDiv(nanoAdjustment, NANOS_PER_SECOND));

        int nos = (int)Math.floorMod(nanoAdjustment, NANOS_PER_SECOND);

        return create(secs, nos);

    }

    /**

     * Obtains an instance of {@code Instant} using milliseconds from the

     * epoch of 1970-01-01T00:00:00Z.

     * <p>

     * The seconds and nanoseconds are extracted from the specified milliseconds.

     *

     * @param epochMilli  the number of milliseconds from 1970-01-01T00:00:00Z

     * @return an instant, not null

     * @throws DateTimeException if the instant exceeds the maximum or minimum instant

     */

    public static Instant ofEpochMilli(long epochMilli) {

        long secs = Math.floorDiv(epochMilli, 1000);

        int mos = Math.floorMod(epochMilli, 1000);

        return create(secs, mos * 1000_000);

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Instant} from a temporal object.

     * <p>

     * This obtains an instant based on the specified temporal.

     * A {@code TemporalAccessor} represents an arbitrary set of date and time information,

     * which this factory converts to an instance of {@code Instant}.

     * <p>

     * The conversion extracts the {@link ChronoField#INSTANT_SECONDS INSTANT_SECONDS}

     * and {@link ChronoField#NANO_OF_SECOND NANO_OF_SECOND} fields.

     * <p>

     * This method matches the signature of the functional interface {@link TemporalQuery}

     * allowing it to be used as a query via method reference, {@code Instant::from}.

     *

     * @param temporal  the temporal object to convert, not null

     * @return the instant, not null

     * @throws DateTimeException if unable to convert to an {@code Instant}

     */

    public static Instant from(TemporalAccessor temporal) {

        if (temporal instanceof Instant) {

            return (Instant) temporal;

        }

        Objects.requireNonNull(temporal, "temporal");

        try {

            long instantSecs = temporal.getLong(INSTANT_SECONDS);

            int nanoOfSecond = temporal.get(NANO_OF_SECOND);

            return Instant.ofEpochSecond(instantSecs, nanoOfSecond);

        } catch (DateTimeException ex) {

            throw new DateTimeException("Unable to obtain Instant from TemporalAccessor: " +

                    temporal + " of type " + temporal.getClass().getName(), ex);

        }

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Instant} from a text string such as

     * {@code 2007-12-03T10:15:30.00Z}.

     * <p>

     * The string must represent a valid instant in UTC and is parsed using

     * {@link DateTimeFormatter#ISO_INSTANT}.

     *

     * @param text  the text to parse, not null

     * @return the parsed instant, not null

     * @throws DateTimeParseException if the text cannot be parsed

     */

    public static Instant parse(final CharSequence text) {

        return DateTimeFormatter.ISO_INSTANT.parse(text, Instant::from);

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Instant} using seconds and nanoseconds.

     *

     * @param seconds  the length of the duration in seconds

     * @param nanoOfSecond  the nano-of-second, from 0 to 999,999,999

     * @throws DateTimeException if the instant exceeds the maximum or minimum instant

     */

    private static Instant create(long seconds, int nanoOfSecond) {

        if ((seconds | nanoOfSecond) == 0) {

            return EPOCH;

        }

        if (seconds < MIN_SECOND || seconds > MAX_SECOND) {

            throw new DateTimeException("Instant exceeds minimum or maximum instant");

        }

        return new Instant(seconds, nanoOfSecond);

    }

    /**

     * Constructs an instance of {@code Instant} using seconds from the epoch of

     * 1970-01-01T00:00:00Z and nanosecond fraction of second.

     *

     * @param epochSecond  the number of seconds from 1970-01-01T00:00:00Z

     * @param nanos  the nanoseconds within the second, must be positive

     */

    private Instant(long epochSecond, int nanos) {

        super();

        this.seconds = epochSecond;

        this.nanos = nanos;

    }

    //-----------------------------------------------------------------------

    /**

     * Checks if the specified field is supported.

     * <p>

     * This checks if this instant can be queried for the specified field.

     * If false, then calling the {@link #range(TemporalField) range},

     * {@link #get(TemporalField) get} and {@link #with(TemporalField, long)}

     * methods will throw an exception.

     * <p>

     * If the field is a {@link ChronoField} then the query is implemented here.

     * The supported fields are:

     * <ul>

     * <li>{@code NANO_OF_SECOND}

     * <li>{@code MICRO_OF_SECOND}

     * <li>{@code MILLI_OF_SECOND}

     * <li>{@code INSTANT_SECONDS}

     * </ul>

     * All other {@code ChronoField} instances will return false.

     * <p>

     * If the field is not a {@code ChronoField}, then the result of this method

     * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}

     * passing {@code this} as the argument.

     * Whether the field is supported is determined by the field.

     *

     * @param field  the field to check, null returns false

     * @return true if the field is supported on this instant, false if not

     */

    @Override

    public boolean isSupported(TemporalField field) {

        if (field instanceof ChronoField) {

            return field == INSTANT_SECONDS || field == NANO_OF_SECOND || field == MICRO_OF_SECOND || field == MILLI_OF_SECOND;

        }

        return field != null && field.isSupportedBy(this);

    }

    /**

     * Checks if the specified unit is supported.

     * <p>

     * This checks if the specified unit can be added to, or subtracted from, this date-time.

     * If false, then calling the {@link #plus(long, TemporalUnit)} and

     * {@link #minus(long, TemporalUnit) minus} methods will throw an exception.

     * <p>

     * If the unit is a {@link ChronoUnit} then the query is implemented here.

     * The supported units are:

     * <ul>

     * <li>{@code NANOS}

     * <li>{@code MICROS}

     * <li>{@code MILLIS}

     * <li>{@code SECONDS}

     * <li>{@code MINUTES}

     * <li>{@code HOURS}

     * <li>{@code HALF_DAYS}

     * <li>{@code DAYS}

     * </ul>

     * All other {@code ChronoUnit} instances will return false.

     * <p>

     * If the unit is not a {@code ChronoUnit}, then the result of this method

     * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}

     * passing {@code this} as the argument.

     * Whether the unit is supported is determined by the unit.

     *

     * @param unit  the unit to check, null returns false

     * @return true if the unit can be added/subtracted, false if not

     */

    @Override

    public boolean isSupported(TemporalUnit unit) {

        if (unit instanceof ChronoUnit) {

            return unit.isTimeBased() || unit == DAYS;

        }

        return unit != null && unit.isSupportedBy(this);

    }

    //-----------------------------------------------------------------------

    /**

     * Gets the range of valid values for the specified field.

     * <p>

     * The range object expresses the minimum and maximum valid values for a field.

     * This instant is used to enhance the accuracy of the returned range.

     * If it is not possible to return the range, because the field is not supported

     * or for some other reason, an exception is thrown.

     * <p>

     * If the field is a {@link ChronoField} then the query is implemented here.

     * The {@link #isSupported(TemporalField) supported fields} will return

     * appropriate range instances.

     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.

     * <p>

     * If the field is not a {@code ChronoField}, then the result of this method

     * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}

     * passing {@code this} as the argument.

     * Whether the range can be obtained is determined by the field.

     *

     * @param field  the field to query the range for, not null

     * @return the range of valid values for the field, not null

     * @throws DateTimeException if the range for the field cannot be obtained

     * @throws UnsupportedTemporalTypeException if the field is not supported

     */

    @Override  // override for Javadoc

    public ValueRange range(TemporalField field) {

        return Temporal.super.range(field);

    }

    /**

     * Gets the value of the specified field from this instant as an {@code int}.

     * <p>

     * This queries this instant for the value of the specified field.

     * The returned value will always be within the valid range of values for the field.

     * If it is not possible to return the value, because the field is not supported

     * or for some other reason, an exception is thrown.

     * <p>

     * If the field is a {@link ChronoField} then the query is implemented here.

     * The {@link #isSupported(TemporalField) supported fields} will return valid

     * values based on this date-time, except {@code INSTANT_SECONDS} which is too

     * large to fit in an {@code int} and throws a {@code DateTimeException}.

     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.

     * <p>

     * If the field is not a {@code ChronoField}, then the result of this method

     * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}

     * passing {@code this} as the argument. Whether the value can be obtained,

     * and what the value represents, is determined by the field.

     *

     * @param field  the field to get, not null

     * @return the value for the field

     * @throws DateTimeException if a value for the field cannot be obtained or

     *         the value is outside the range of valid values for the field

     * @throws UnsupportedTemporalTypeException if the field is not supported or

     *         the range of values exceeds an {@code int}

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override  // override for Javadoc and performance

    public int get(TemporalField field) {

        if (field instanceof ChronoField) {

            switch ((ChronoField) field) {

                case NANO_OF_SECOND: return nanos;

                case MICRO_OF_SECOND: return nanos / 1000;

                case MILLI_OF_SECOND: return nanos / 1000_000;

            }

            throw new UnsupportedTemporalTypeException("Unsupported field: " + field);

        }

        return range(field).checkValidIntValue(field.getFrom(this), field);

    }

    /**

     * Gets the value of the specified field from this instant as a {@code long}.

     * <p>

     * This queries this instant for the value of the specified field.

     * If it is not possible to return the value, because the field is not supported

     * or for some other reason, an exception is thrown.

     * <p>

     * If the field is a {@link ChronoField} then the query is implemented here.

     * The {@link #isSupported(TemporalField) supported fields} will return valid

     * values based on this date-time.

     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.

     * <p>

     * If the field is not a {@code ChronoField}, then the result of this method

     * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}

     * passing {@code this} as the argument. Whether the value can be obtained,

     * and what the value represents, is determined by the field.

     *

     * @param field  the field to get, not null

     * @return the value for the field

     * @throws DateTimeException if a value for the field cannot be obtained

     * @throws UnsupportedTemporalTypeException if the field is not supported

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public long getLong(TemporalField field) {

        if (field instanceof ChronoField) {

            switch ((ChronoField) field) {

                case NANO_OF_SECOND: return nanos;

                case MICRO_OF_SECOND: return nanos / 1000;

                case MILLI_OF_SECOND: return nanos / 1000_000;

                case INSTANT_SECONDS: return seconds;

            }

            throw new UnsupportedTemporalTypeException("Unsupported field: " + field);

        }

        return field.getFrom(this);

    }

    //-----------------------------------------------------------------------

    /**

     * Gets the number of seconds from the Java epoch of 1970-01-01T00:00:00Z.

     * <p>

     * The epoch second count is a simple incrementing count of seconds where

     * second 0 is 1970-01-01T00:00:00Z.

     * The nanosecond part is returned by {@link #getNano}.

     *

     * @return the seconds from the epoch of 1970-01-01T00:00:00Z

     */

    public long getEpochSecond() {

        return seconds;

    }

    /**

     * Gets the number of nanoseconds, later along the time-line, from the start

     * of the second.

     * <p>

     * The nanosecond-of-second value measures the total number of nanoseconds from

     * the second returned by {@link #getEpochSecond}.

     *

     * @return the nanoseconds within the second, always positive, never exceeds 999,999,999

     */

    public int getNano() {

        return nanos;

    }

    //-------------------------------------------------------------------------

    /**

     * Returns an adjusted copy of this instant.

     * <p>

     * This returns an {@code Instant}, based on this one, with the instant adjusted.

     * The adjustment takes place using the specified adjuster strategy object.

     * Read the documentation of the adjuster to understand what adjustment will be made.

     * <p>

     * The result of this method is obtained by invoking the

     * {@link TemporalAdjuster#adjustInto(Temporal)} method on the

     * specified adjuster passing {@code this} as the argument.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param adjuster the adjuster to use, not null

     * @return an {@code Instant} based on {@code this} with the adjustment made, not null

     * @throws DateTimeException if the adjustment cannot be made

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Instant with(TemporalAdjuster adjuster) {

        return (Instant) adjuster.adjustInto(this);

    }

    /**

     * Returns a copy of this instant with the specified field set to a new value.

     * <p>

     * This returns an {@code Instant}, based on this one, with the value

     * for the specified field changed.

     * If it is not possible to set the value, because the field is not supported or for

     * some other reason, an exception is thrown.

     * <p>

     * If the field is a {@link ChronoField} then the adjustment is implemented here.

     * The supported fields behave as follows:

     * <ul>

     * <li>{@code NANO_OF_SECOND} -

     *  Returns an {@code Instant} with the specified nano-of-second.

     *  The epoch-second will be unchanged.

     * <li>{@code MICRO_OF_SECOND} -

     *  Returns an {@code Instant} with the nano-of-second replaced by the specified

     *  micro-of-second multiplied by 1,000. The epoch-second will be unchanged.

     * <li>{@code MILLI_OF_SECOND} -

     *  Returns an {@code Instant} with the nano-of-second replaced by the specified

     *  milli-of-second multiplied by 1,000,000. The epoch-second will be unchanged.

     * <li>{@code INSTANT_SECONDS} -

     *  Returns an {@code Instant} with the specified epoch-second.

     *  The nano-of-second will be unchanged.

     * </ul>

     * <p>

     * In all cases, if the new value is outside the valid range of values for the field

     * then a {@code DateTimeException} will be thrown.

     * <p>

     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.

     * <p>

     * If the field is not a {@code ChronoField}, then the result of this method

     * is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)}

     * passing {@code this} as the argument. In this case, the field determines

     * whether and how to adjust the instant.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param field  the field to set in the result, not null

     * @param newValue  the new value of the field in the result

     * @return an {@code Instant} based on {@code this} with the specified field set, not null

     * @throws DateTimeException if the field cannot be set

     * @throws UnsupportedTemporalTypeException if the field is not supported

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Instant with(TemporalField field, long newValue) {

        if (field instanceof ChronoField) {

            ChronoField f = (ChronoField) field;

            f.checkValidValue(newValue);

            switch (f) {

                case MILLI_OF_SECOND: {

                    int nval = (int) newValue * 1000_000;

                    return (nval != nanos ? create(seconds, nval) : this);

                }

                case MICRO_OF_SECOND: {

                    int nval = (int) newValue * 1000;

                    return (nval != nanos ? create(seconds, nval) : this);

                }

                case NANO_OF_SECOND: return (newValue != nanos ? create(seconds, (int) newValue) : this);

                case INSTANT_SECONDS: return (newValue != seconds ? create(newValue, nanos) : this);

            }

            throw new UnsupportedTemporalTypeException("Unsupported field: " + field);

        }

        return field.adjustInto(this, newValue);

    }

    //-----------------------------------------------------------------------

    /**

     * Returns a copy of this {@code Instant} truncated to the specified unit.

     * <p>

     * Truncating the instant returns a copy of the original with fields

     * smaller than the specified unit set to zero.

     * The fields are calculated on the basis of using a UTC offset as seen

     * in {@code toString}.

     * For example, truncating with the {@link ChronoUnit#MINUTES MINUTES} unit will

     * round down to the nearest minute, setting the seconds and nanoseconds to zero.

     * <p>

     * The unit must have a {@linkplain TemporalUnit#getDuration() duration}

     * that divides into the length of a standard day without remainder.

     * This includes all supplied time units on {@link ChronoUnit} and

     * {@link ChronoUnit#DAYS DAYS}. Other units throw an exception.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param unit  the unit to truncate to, not null

     * @return an {@code Instant} based on this instant with the time truncated, not null

     * @throws DateTimeException if the unit is invalid for truncation

     * @throws UnsupportedTemporalTypeException if the unit is not supported

     */

    public Instant truncatedTo(TemporalUnit unit) {

        if (unit == ChronoUnit.NANOS) {

            return this;

        }

        Duration unitDur = unit.getDuration();

        if (unitDur.getSeconds() > LocalTime.SECONDS_PER_DAY) {

            throw new UnsupportedTemporalTypeException("Unit is too large to be used for truncation");

        }

        long dur = unitDur.toNanos();

        if ((LocalTime.NANOS_PER_DAY % dur) != 0) {

            throw new UnsupportedTemporalTypeException("Unit must divide into a standard day without remainder");

        }

        long nod = (seconds % LocalTime.SECONDS_PER_DAY) * LocalTime.NANOS_PER_SECOND + nanos;

        long result = Math.floorDiv(nod, dur) * dur;

        return plusNanos(result - nod);

    }

    //-----------------------------------------------------------------------

    /**

     * Returns a copy of this instant with the specified amount added.

     * <p>

     * This returns an {@code Instant}, based on this one, with the specified amount added.

     * The amount is typically {@link Duration} but may be any other type implementing

     * the {@link TemporalAmount} interface.

     * <p>

     * The calculation is delegated to the amount object by calling

     * {@link TemporalAmount#addTo(Temporal)}. The amount implementation is free

     * to implement the addition in any way it wishes, however it typically

     * calls back to {@link #plus(long, TemporalUnit)}. Consult the documentation

     * of the amount implementation to determine if it can be successfully added.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param amountToAdd  the amount to add, not null

     * @return an {@code Instant} based on this instant with the addition made, not null

     * @throws DateTimeException if the addition cannot be made

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Instant plus(TemporalAmount amountToAdd) {

        return (Instant) amountToAdd.addTo(this);

    }

    /**

     * Returns a copy of this instant with the specified amount added.

     * <p>

     * This returns an {@code Instant}, based on this one, with the amount

     * in terms of the unit added. If it is not possible to add the amount, because the

     * unit is not supported or for some other reason, an exception is thrown.

     * <p>

     * If the field is a {@link ChronoUnit} then the addition is implemented here.

     * The supported fields behave as follows:

     * <ul>

     * <li>{@code NANOS} -

     *  Returns an {@code Instant} with the specified number of nanoseconds added.

     *  This is equivalent to {@link #plusNanos(long)}.

     * <li>{@code MICROS} -

     *  Returns an {@code Instant} with the specified number of microseconds added.

     *  This is equivalent to {@link #plusNanos(long)} with the amount

     *  multiplied by 1,000.

     * <li>{@code MILLIS} -

     *  Returns an {@code Instant} with the specified number of milliseconds added.

     *  This is equivalent to {@link #plusNanos(long)} with the amount

     *  multiplied by 1,000,000.

     * <li>{@code SECONDS} -

     *  Returns an {@code Instant} with the specified number of seconds added.

     *  This is equivalent to {@link #plusSeconds(long)}.

     * <li>{@code MINUTES} -

     *  Returns an {@code Instant} with the specified number of minutes added.

     *  This is equivalent to {@link #plusSeconds(long)} with the amount

     *  multiplied by 60.

     * <li>{@code HOURS} -

     *  Returns an {@code Instant} with the specified number of hours added.

     *  This is equivalent to {@link #plusSeconds(long)} with the amount

     *  multiplied by 3,600.

     * <li>{@code HALF_DAYS} -

     *  Returns an {@code Instant} with the specified number of half-days added.

     *  This is equivalent to {@link #plusSeconds(long)} with the amount

     *  multiplied by 43,200 (12 hours).

     * <li>{@code DAYS} -

     *  Returns an {@code Instant} with the specified number of days added.

     *  This is equivalent to {@link #plusSeconds(long)} with the amount

     *  multiplied by 86,400 (24 hours).

     * </ul>

     * <p>

     * All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}.

     * <p>

     * If the field is not a {@code ChronoUnit}, then the result of this method

     * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)}

     * passing {@code this} as the argument. In this case, the unit determines

     * whether and how to perform the addition.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param amountToAdd  the amount of the unit to add to the result, may be negative

     * @param unit  the unit of the amount to add, not null

     * @return an {@code Instant} based on this instant with the specified amount added, not null

     * @throws DateTimeException if the addition cannot be made

     * @throws UnsupportedTemporalTypeException if the unit is not supported

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Instant plus(long amountToAdd, TemporalUnit unit) {

        if (unit instanceof ChronoUnit) {

            switch ((ChronoUnit) unit) {

                case NANOS: return plusNanos(amountToAdd);

                case MICROS: return plus(amountToAdd / 1000_000, (amountToAdd % 1000_000) * 1000);

                case MILLIS: return plusMillis(amountToAdd);

                case SECONDS: return plusSeconds(amountToAdd);

                case MINUTES: return plusSeconds(Math.multiplyExact(amountToAdd, SECONDS_PER_MINUTE));

                case HOURS: return plusSeconds(Math.multiplyExact(amountToAdd, SECONDS_PER_HOUR));

                case HALF_DAYS: return plusSeconds(Math.multiplyExact(amountToAdd, SECONDS_PER_DAY / 2));

                case DAYS: return plusSeconds(Math.multiplyExact(amountToAdd, SECONDS_PER_DAY));

            }

            throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);

        }

        return unit.addTo(this, amountToAdd);

    }

    //-----------------------------------------------------------------------

    /**

     * Returns a copy of this instant with the specified duration in seconds added.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param secondsToAdd  the seconds to add, positive or negative

     * @return an {@code Instant} based on this instant with the specified seconds added, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public Instant plusSeconds(long secondsToAdd) {

        return plus(secondsToAdd, 0);

    }

    /**

     * Returns a copy of this instant with the specified duration in milliseconds added.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param millisToAdd  the milliseconds to add, positive or negative

     * @return an {@code Instant} based on this instant with the specified milliseconds added, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public Instant plusMillis(long millisToAdd) {

        return plus(millisToAdd / 1000, (millisToAdd % 1000) * 1000_000);

    }

    /**

     * Returns a copy of this instant with the specified duration in nanoseconds added.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param nanosToAdd  the nanoseconds to add, positive or negative

     * @return an {@code Instant} based on this instant with the specified nanoseconds added, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public Instant plusNanos(long nanosToAdd) {

        return plus(0, nanosToAdd);

    }

    /**

     * Returns a copy of this instant with the specified duration added.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param secondsToAdd  the seconds to add, positive or negative

     * @param nanosToAdd  the nanos to add, positive or negative

     * @return an {@code Instant} based on this instant with the specified seconds added, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    private Instant plus(long secondsToAdd, long nanosToAdd) {

        if ((secondsToAdd | nanosToAdd) == 0) {

            return this;

        }

        long epochSec = Math.addExact(seconds, secondsToAdd);

        epochSec = Math.addExact(epochSec, nanosToAdd / NANOS_PER_SECOND);

        nanosToAdd = nanosToAdd % NANOS_PER_SECOND;

        long nanoAdjustment = nanos + nanosToAdd;  // safe int+NANOS_PER_SECOND

        return ofEpochSecond(epochSec, nanoAdjustment);

    }

    //-----------------------------------------------------------------------

    /**

     * Returns a copy of this instant with the specified amount subtracted.

     * <p>

     * This returns an {@code Instant}, based on this one, with the specified amount subtracted.

     * The amount is typically {@link Duration} but may be any other type implementing

     * the {@link TemporalAmount} interface.

     * <p>

     * The calculation is delegated to the amount object by calling

     * {@link TemporalAmount#subtractFrom(Temporal)}. The amount implementation is free

     * to implement the subtraction in any way it wishes, however it typically

     * calls back to {@link #minus(long, TemporalUnit)}. Consult the documentation

     * of the amount implementation to determine if it can be successfully subtracted.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param amountToSubtract  the amount to subtract, not null

     * @return an {@code Instant} based on this instant with the subtraction made, not null

     * @throws DateTimeException if the subtraction cannot be made

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Instant minus(TemporalAmount amountToSubtract) {

        return (Instant) amountToSubtract.subtractFrom(this);

    }

    /**

     * Returns a copy of this instant with the specified amount subtracted.

     * <p>

     * This returns an {@code Instant}, based on this one, with the amount

     * in terms of the unit subtracted. If it is not possible to subtract the amount,

     * because the unit is not supported or for some other reason, an exception is thrown.

     * <p>

     * This method is equivalent to {@link #plus(long, TemporalUnit)} with the amount negated.

     * See that method for a full description of how addition, and thus subtraction, works.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param amountToSubtract  the amount of the unit to subtract from the result, may be negative

     * @param unit  the unit of the amount to subtract, not null

     * @return an {@code Instant} based on this instant with the specified amount subtracted, not null

     * @throws DateTimeException if the subtraction cannot be made

     * @throws UnsupportedTemporalTypeException if the unit is not supported

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Instant minus(long amountToSubtract, TemporalUnit unit) {

        return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));

    }

    //-----------------------------------------------------------------------

    /**

     * Returns a copy of this instant with the specified duration in seconds subtracted.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param secondsToSubtract  the seconds to subtract, positive or negative

     * @return an {@code Instant} based on this instant with the specified seconds subtracted, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public Instant minusSeconds(long secondsToSubtract) {

        if (secondsToSubtract == Long.MIN_VALUE) {

            return plusSeconds(Long.MAX_VALUE).plusSeconds(1);

        }

        return plusSeconds(-secondsToSubtract);

    }

    /**

     * Returns a copy of this instant with the specified duration in milliseconds subtracted.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param millisToSubtract  the milliseconds to subtract, positive or negative

     * @return an {@code Instant} based on this instant with the specified milliseconds subtracted, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public Instant minusMillis(long millisToSubtract) {

        if (millisToSubtract == Long.MIN_VALUE) {

            return plusMillis(Long.MAX_VALUE).plusMillis(1);

        }

        return plusMillis(-millisToSubtract);

    }

    /**

     * Returns a copy of this instant with the specified duration in nanoseconds subtracted.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param nanosToSubtract  the nanoseconds to subtract, positive or negative

     * @return an {@code Instant} based on this instant with the specified nanoseconds subtracted, not null

     * @throws DateTimeException if the result exceeds the maximum or minimum instant

     * @throws ArithmeticException if numeric overflow occurs

     */

    public Instant minusNanos(long nanosToSubtract) {

        if (nanosToSubtract == Long.MIN_VALUE) {

            return plusNanos(Long.MAX_VALUE).plusNanos(1);

        }

        return plusNanos(-nanosToSubtract);

    }

    //-------------------------------------------------------------------------

    /**

     * Queries this instant using the specified query.

     * <p>

     * This queries this instant using the specified query strategy object.

     * The {@code TemporalQuery} object defines the logic to be used to

     * obtain the result. Read the documentation of the query to understand

     * what the result of this method will be.

     * <p>

     * The result of this method is obtained by invoking the

     * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the

     * specified query passing {@code this} as the argument.

     *

     * @param <R> the type of the result

     * @param query  the query to invoke, not null

     * @return the query result, null may be returned (defined by the query)

     * @throws DateTimeException if unable to query (defined by the query)

     * @throws ArithmeticException if numeric overflow occurs (defined by the query)

     */

    @SuppressWarnings("unchecked")

    @Override

    public <R> R query(TemporalQuery<R> query) {

        if (query == TemporalQueries.precision()) {

            return (R) NANOS;

        }

        // inline TemporalAccessor.super.query(query) as an optimization

        if (query == TemporalQueries.chronology() || query == TemporalQueries.zoneId() ||

                query == TemporalQueries.zone() || query == TemporalQueries.offset() ||

                query == TemporalQueries.localDate() || query == TemporalQueries.localTime()) {

            return null;

        }

        return query.queryFrom(this);

    }

    /**

     * Adjusts the specified temporal object to have this instant.

     * <p>

     * This returns a temporal object of the same observable type as the input

     * with the instant changed to be the same as this.

     * <p>

     * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}

     * twice, passing {@link ChronoField#INSTANT_SECONDS} and

     * {@link ChronoField#NANO_OF_SECOND} as the fields.

     * <p>

     * In most cases, it is clearer to reverse the calling pattern by using

     * {@link Temporal#with(TemporalAdjuster)}:

     * <pre>

     *   // these two lines are equivalent, but the second approach is recommended

     *   temporal = thisInstant.adjustInto(temporal);

     *   temporal = temporal.with(thisInstant);

     * </pre>

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param temporal  the target object to be adjusted, not null

     * @return the adjusted object, not null

     * @throws DateTimeException if unable to make the adjustment

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public Temporal adjustInto(Temporal temporal) {

        return temporal.with(INSTANT_SECONDS, seconds).with(NANO_OF_SECOND, nanos);

    }

    /**

     * Calculates the amount of time until another instant in terms of the specified unit.

     * <p>

     * This calculates the amount of time between two {@code Instant}

     * objects in terms of a single {@code TemporalUnit}.

     * The start and end points are {@code this} and the specified instant.

     * The result will be negative if the end is before the start.

     * The calculation returns a whole number, representing the number of

     * complete units between the two instants.

     * The {@code Temporal} passed to this method is converted to a

     * {@code Instant} using {@link #from(TemporalAccessor)}.

     * For example, the amount in seconds between two dates can be calculated

     * using {@code startInstant.until(endInstant, SECONDS)}.

     * <p>

     * There are two equivalent ways of using this method.

     * The first is to invoke this method.

     * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:

     * <pre>

     *   // these two lines are equivalent

     *   amount = start.until(end, SECONDS);

     *   amount = SECONDS.between(start, end);

     * </pre>

     * The choice should be made based on which makes the code more readable.

     * <p>

     * The calculation is implemented in this method for {@link ChronoUnit}.

     * The units {@code NANOS}, {@code MICROS}, {@code MILLIS}, {@code SECONDS},

     * {@code MINUTES}, {@code HOURS}, {@code HALF_DAYS} and {@code DAYS}

     * are supported. Other {@code ChronoUnit} values will throw an exception.

     * <p>

     * If the unit is not a {@code ChronoUnit}, then the result of this method

     * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}

     * passing {@code this} as the first argument and the converted input temporal

     * as the second argument.

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param endExclusive  the end date, exclusive, which is converted to an {@code Instant}, not null

     * @param unit  the unit to measure the amount in, not null

     * @return the amount of time between this instant and the end instant

     * @throws DateTimeException if the amount cannot be calculated, or the end

     *  temporal cannot be converted to an {@code Instant}

     * @throws UnsupportedTemporalTypeException if the unit is not supported

     * @throws ArithmeticException if numeric overflow occurs

     */

    @Override

    public long until(Temporal endExclusive, TemporalUnit unit) {

        Instant end = Instant.from(endExclusive);

        if (unit instanceof ChronoUnit) {

            ChronoUnit f = (ChronoUnit) unit;

            switch (f) {

                case NANOS: return nanosUntil(end);

                case MICROS: return nanosUntil(end) / 1000;

                case MILLIS: return Math.subtractExact(end.toEpochMilli(), toEpochMilli());

                case SECONDS: return secondsUntil(end);

                case MINUTES: return secondsUntil(end) / SECONDS_PER_MINUTE;

                case HOURS: return secondsUntil(end) / SECONDS_PER_HOUR;

                case HALF_DAYS: return secondsUntil(end) / (12 * SECONDS_PER_HOUR);

                case DAYS: return secondsUntil(end) / (SECONDS_PER_DAY);

            }

            throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);

        }

        return unit.between(this, end);

    }

    private long nanosUntil(Instant end) {

        long secsDiff = Math.subtractExact(end.seconds, seconds);

        long totalNanos = Math.multiplyExact(secsDiff, NANOS_PER_SECOND);

        return Math.addExact(totalNanos, end.nanos - nanos);

    }

    private long secondsUntil(Instant end) {

        long secsDiff = Math.subtractExact(end.seconds, seconds);

        long nanosDiff = end.nanos - nanos;

        if (secsDiff > 0 && nanosDiff < 0) {

            secsDiff--;

        } else if (secsDiff < 0 && nanosDiff > 0) {

            secsDiff++;

        }

        return secsDiff;

    }

    //-----------------------------------------------------------------------

    /**

     * Combines this instant with an offset to create an {@code OffsetDateTime}.

     * <p>

     * This returns an {@code OffsetDateTime} formed from this instant at the

     * specified offset from UTC/Greenwich. An exception will be thrown if the

     * instant is too large to fit into an offset date-time.

     * <p>

     * This method is equivalent to

     * {@link OffsetDateTime#ofInstant(Instant, ZoneId) OffsetDateTime.ofInstant(this, offset)}.

     *

     * @param offset  the offset to combine with, not null

     * @return the offset date-time formed from this instant and the specified offset, not null

     * @throws DateTimeException if the result exceeds the supported range

     */

    public OffsetDateTime atOffset(ZoneOffset offset) {

        return OffsetDateTime.ofInstant(this, offset);

    }

    /**

     * Combines this instant with a time-zone to create a {@code ZonedDateTime}.

     * <p>

     * This returns an {@code ZonedDateTime} formed from this instant at the

     * specified time-zone. An exception will be thrown if the instant is too

     * large to fit into a zoned date-time.

     * <p>

     * This method is equivalent to

     * {@link ZonedDateTime#ofInstant(Instant, ZoneId) ZonedDateTime.ofInstant(this, zone)}.

     *

     * @param zone  the zone to combine with, not null

     * @return the zoned date-time formed from this instant and the specified zone, not null

     * @throws DateTimeException if the result exceeds the supported range

     */