Back to index...

	/*
	* Copyright (c) 1996, 2021, 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.
	*/

	/*
	* (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
	* (C) Copyright IBM Corp. 1996 - All Rights Reserved
	*
	* The original version of this source code and documentation is copyrighted
	* and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
	* materials are provided under terms of a License Agreement between Taligent
	* and Sun. This technology is protected by multiple US and International
	* patents. This notice and attribution to Taligent may not be removed.
	* Taligent is a registered trademark of Taligent, Inc.
	*
	*/

	package java.util;

	import java.io.Serializable;
	import java.time.ZoneId;

	import jdk.internal.util.StaticProperty;
	import sun.security.action.GetPropertyAction;
	import sun.util.calendar.ZoneInfo;
	import sun.util.calendar.ZoneInfoFile;
	import sun.util.locale.provider.TimeZoneNameUtility;

	/**
	* {@code TimeZone} represents a time zone offset, and also figures out daylight
	* savings.
	*
	* <p>
	* Typically, you get a {@code TimeZone} using {@code getDefault}
	* which creates a {@code TimeZone} based on the time zone where the program
	* is running. For example, for a program running in Japan, {@code getDefault}
	* creates a {@code TimeZone} object based on Japanese Standard Time.
	*
	* <p>
	* You can also get a {@code TimeZone} using {@code getTimeZone}
	* along with a time zone ID. For instance, the time zone ID for the
	* U.S. Pacific Time zone is "America/Los_Angeles". So, you can get a
	* U.S. Pacific Time {@code TimeZone} object with:
	* <blockquote><pre>
	* TimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
	* </pre></blockquote>
	* You can use the {@code getAvailableIDs} method to iterate through
	* all the supported time zone IDs. You can then choose a
	* supported ID to get a {@code TimeZone}.
	* If the time zone you want is not represented by one of the
	* supported IDs, then a custom time zone ID can be specified to
	* produce a TimeZone. The syntax of a custom time zone ID is:
	*
	* <blockquote><pre>
	* <a id="CustomID"><i>CustomID:</i></a>
	* {@code GMT} <i>Sign</i> <i>Hours</i> {@code :} <i>Minutes</i>
	* {@code GMT} <i>Sign</i> <i>Hours</i> <i>Minutes</i>
	* {@code GMT} <i>Sign</i> <i>Hours</i>
	* <i>Sign:</i> one of
	* {@code + -}
	* <i>Hours:</i>
	* <i>Digit</i>
	* <i>Digit</i> <i>Digit</i>
	* <i>Minutes:</i>
	* <i>Digit</i> <i>Digit</i>
	* <i>Digit:</i> one of
	* {@code 0 1 2 3 4 5 6 7 8 9}
	* </pre></blockquote>
	*
	* <i>Hours</i> must be between 0 to 23 and <i>Minutes</i> must be
	* between 00 to 59. For example, "GMT+10" and "GMT+0010" mean ten
	* hours and ten minutes ahead of GMT, respectively.
	* <p>
	* The format is locale independent and digits must be taken from the
	* Basic Latin block of the Unicode standard. No daylight saving time
	* transition schedule can be specified with a custom time zone ID. If
	* the specified string doesn't match the syntax, {@code "GMT"}
	* is used.
	* <p>
	* When creating a {@code TimeZone}, the specified custom time
	* zone ID is normalized in the following syntax:
	* <blockquote><pre>
	* <a id="NormalizedCustomID"><i>NormalizedCustomID:</i></a>
	* {@code GMT} <i>Sign</i> <i>TwoDigitHours</i> {@code :} <i>Minutes</i>
	* <i>Sign:</i> one of
	* {@code + -}
	* <i>TwoDigitHours:</i>
	* <i>Digit</i> <i>Digit</i>
	* <i>Minutes:</i>
	* <i>Digit</i> <i>Digit</i>
	* <i>Digit:</i> one of
	* {@code 0 1 2 3 4 5 6 7 8 9}
	* </pre></blockquote>
	* For example, TimeZone.getTimeZone("GMT-8").getID() returns "GMT-08:00".
	*
	* <h2>Three-letter time zone IDs</h2>
	*
	* For compatibility with JDK 1.1.x, some other three-letter time zone IDs
	* (such as "PST", "CTT", "AST") are also supported. However, <strong>their
	* use is deprecated</strong> because the same abbreviation is often used
	* for multiple time zones (for example, "CST" could be U.S. "Central Standard
	* Time" and "China Standard Time"), and the Java platform can then only
	* recognize one of them.
	*
	*
	* @see Calendar
	* @see GregorianCalendar
	* @see SimpleTimeZone
	* @author Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
	* @since 1.1
	*/
	public abstract class TimeZone implements Serializable, Cloneable {
	/**
	* Sole constructor. (For invocation by subclass constructors, typically
	* implicit.)
	*/
	public TimeZone() {
	}

	/**
	* A style specifier for {@code getDisplayName()} indicating
	* a short name, such as "PST."
	* @see #LONG
	* @since 1.2
	*/
	public static final int SHORT = 0;

	/**
	* A style specifier for {@code getDisplayName()} indicating
	* a long name, such as "Pacific Standard Time."
	* @see #SHORT
	* @since 1.2
	*/
	public static final int LONG = 1;

	// Constants used internally; unit is milliseconds
	private static final int ONE_MINUTE = 60*1000;
	private static final int ONE_HOUR = 60*ONE_MINUTE;
	private static final int ONE_DAY = 24*ONE_HOUR;

	// Proclaim serialization compatibility with JDK 1.1
	@java.io.Serial
	static final long serialVersionUID = 3581463369166924961L;

	/**
	* Gets the time zone offset, for current date, modified in case of
	* daylight savings. This is the offset to add to UTC to get local time.
	* <p>
	* This method returns a historically correct offset if an
	* underlying {@code TimeZone} implementation subclass
	* supports historical Daylight Saving Time schedule and GMT
	* offset changes.
	*
	* @param era the era of the given date.
	* @param year the year in the given date.
	* @param month the month in the given date.
	* Month is 0-based. e.g., 0 for January.
	* @param day the day-in-month of the given date.
	* @param dayOfWeek the day-of-week of the given date.
	* @param milliseconds the milliseconds in day in <em>standard</em>
	* local time.
	*
	* @return the offset in milliseconds to add to GMT to get local time.
	*
	* @see Calendar#ZONE_OFFSET
	* @see Calendar#DST_OFFSET
	*/
	public abstract int getOffset(int era, int year, int month, int day,
	int dayOfWeek, int milliseconds);

	/**
	* Returns the offset of this time zone from UTC at the specified
	* date. If Daylight Saving Time is in effect at the specified
	* date, the offset value is adjusted with the amount of daylight
	* saving.
	* <p>
	* This method returns a historically correct offset value if an
	* underlying TimeZone implementation subclass supports historical
	* Daylight Saving Time schedule and GMT offset changes.
	*
	* @param date the date represented in milliseconds since January 1, 1970 00:00:00 GMT
	* @return the amount of time in milliseconds to add to UTC to get local time.
	*
	* @see Calendar#ZONE_OFFSET
	* @see Calendar#DST_OFFSET
	* @since 1.4
	*/
	public int getOffset(long date) {
	if (inDaylightTime(new Date(date))) {
	return getRawOffset() + getDSTSavings();
	}
	return getRawOffset();
	}

	/**
	* Gets the raw GMT offset and the amount of daylight saving of this
	* time zone at the given time.
	* @param date the milliseconds (since January 1, 1970,
	* 00:00:00.000 GMT) at which the time zone offset and daylight
	* saving amount are found
	* @param offsets an array of int where the raw GMT offset
	* (offset[0]) and daylight saving amount (offset[1]) are stored,
	* or null if those values are not needed. The method assumes that
	* the length of the given array is two or larger.
	* @return the total amount of the raw GMT offset and daylight
	* saving at the specified date.
	*
	* @see Calendar#ZONE_OFFSET
	* @see Calendar#DST_OFFSET
	*/
	int getOffsets(long date, int[] offsets) {
	int rawoffset = getRawOffset();
	int dstoffset = 0;
	if (inDaylightTime(new Date(date))) {
	dstoffset = getDSTSavings();
	}
	if (offsets != null) {
	offsets[0] = rawoffset;
	offsets[1] = dstoffset;
	}
	return rawoffset + dstoffset;
	}

	/**
	* Sets the base time zone offset to GMT.
	* This is the offset to add to UTC to get local time.
	* <p>
	* If an underlying {@code TimeZone} implementation subclass
	* supports historical GMT offset changes, the specified GMT
	* offset is set as the latest GMT offset and the difference from
	* the known latest GMT offset value is used to adjust all
	* historical GMT offset values.
	*
	* @param offsetMillis the given base time zone offset to GMT.
	*/
	public abstract void setRawOffset(int offsetMillis);

	/**
	* Returns the amount of time in milliseconds to add to UTC to get
	* standard time in this time zone. Because this value is not
	* affected by daylight saving time, it is called <I>raw
	* offset</I>.
	* <p>
	* If an underlying {@code TimeZone} implementation subclass
	* supports historical GMT offset changes, the method returns the
	* raw offset value of the current date. In Honolulu, for example,
	* its raw offset changed from GMT-10:30 to GMT-10:00 in 1947, and
	* this method always returns -36000000 milliseconds (i.e., -10
	* hours).
	*
	* @return the amount of raw offset time in milliseconds to add to UTC.
	* @see Calendar#ZONE_OFFSET
	*/
	public abstract int getRawOffset();

	/**
	* Gets the ID of this time zone.
	* @return the ID of this time zone.
	*/
	public String getID()
	{
	return ID;
	}

	/**
	* Sets the time zone ID. This does not change any other data in
	* the time zone object.
	* @param ID the new time zone ID.
	*/
	public void setID(String ID)
	{
	if (ID == null) {
	throw new NullPointerException();
	}
	this.ID = ID;
	this.zoneId = null; // invalidate cache
	}

	/**
	* Returns a long standard time name of this {@code TimeZone} suitable for
	* presentation to the user in the default locale.
	*
	* <p>This method is equivalent to:
	* <blockquote><pre>
	* getDisplayName(false, {@link #LONG},
	* Locale.getDefault({@link Locale.Category#DISPLAY}))
	* </pre></blockquote>
	*
	* @return the human-readable name of this time zone in the default locale.
	* @since 1.2
	* @see #getDisplayName(boolean, int, Locale)
	* @see Locale#getDefault(Locale.Category)
	* @see Locale.Category
	*/
	public final String getDisplayName() {
	return getDisplayName(false, LONG,
	Locale.getDefault(Locale.Category.DISPLAY));
	}

	/**
	* Returns a long standard time name of this {@code TimeZone} suitable for
	* presentation to the user in the specified {@code locale}.
	*
	* <p>This method is equivalent to:
	* <blockquote><pre>
	* getDisplayName(false, {@link #LONG}, locale)
	* </pre></blockquote>
	*
	* @param locale the locale in which to supply the display name.
	* @return the human-readable name of this time zone in the given locale.
	* @throws NullPointerException if {@code locale} is {@code null}.
	* @since 1.2
	* @see #getDisplayName(boolean, int, Locale)
	*/
	public final String getDisplayName(Locale locale) {
	return getDisplayName(false, LONG, locale);
	}

	/**
	* Returns a name in the specified {@code style} of this {@code TimeZone}
	* suitable for presentation to the user in the default locale. If the
	* specified {@code daylight} is {@code true}, a Daylight Saving Time name
	* is returned (even if this {@code TimeZone} doesn't observe Daylight Saving
	* Time). Otherwise, a Standard Time name is returned.
	*
	* <p>This method is equivalent to:
	* <blockquote><pre>
	* getDisplayName(daylight, style,
	* Locale.getDefault({@link Locale.Category#DISPLAY}))
	* </pre></blockquote>
	*
	* @param daylight {@code true} specifying a Daylight Saving Time name, or
	* {@code false} specifying a Standard Time name
	* @param style either {@link #LONG} or {@link #SHORT}
	* @return the human-readable name of this time zone in the default locale.
	* @throws IllegalArgumentException if {@code style} is invalid.
	* @since 1.2
	* @see #getDisplayName(boolean, int, Locale)
	* @see Locale#getDefault(Locale.Category)
	* @see Locale.Category
	* @see java.text.DateFormatSymbols#getZoneStrings()
	*/
	public final String getDisplayName(boolean daylight, int style) {
	return getDisplayName(daylight, style,
	Locale.getDefault(Locale.Category.DISPLAY));
	}

	/**
	* Returns a name in the specified {@code style} of this {@code TimeZone}
	* suitable for presentation to the user in the specified {@code
	* locale}. If the specified {@code daylight} is {@code true}, a Daylight
	* Saving Time name is returned (even if this {@code TimeZone} doesn't
	* observe Daylight Saving Time). Otherwise, a Standard Time name is
	* returned.
	*
	* <p>When looking up a time zone name, the {@linkplain
	* ResourceBundle.Control#getCandidateLocales(String,Locale) default
	* {@code Locale} search path of {@code ResourceBundle}} derived
	* from the specified {@code locale} is used. (No {@linkplain
	* ResourceBundle.Control#getFallbackLocale(String,Locale) fallback
	* {@code Locale}} search is performed.) If a time zone name in any
	* {@code Locale} of the search path, including {@link Locale#ROOT}, is
	* found, the name is returned. Otherwise, a string in the
	* <a href="#NormalizedCustomID">normalized custom ID format</a> is returned.
	*
	* @param daylight {@code true} specifying a Daylight Saving Time name, or
	* {@code false} specifying a Standard Time name
	* @param style either {@link #LONG} or {@link #SHORT}
	* @param locale the locale in which to supply the display name.
	* @return the human-readable name of this time zone in the given locale.
	* @throws IllegalArgumentException if {@code style} is invalid.
	* @throws NullPointerException if {@code locale} is {@code null}.
	* @since 1.2
	* @see java.text.DateFormatSymbols#getZoneStrings()
	*/
	public String getDisplayName(boolean daylight, int style, Locale locale) {
	if (style != SHORT && style != LONG) {
	throw new IllegalArgumentException("Illegal style: " + style);
	}
	String id = getID();
	String name = TimeZoneNameUtility.retrieveDisplayName(id, daylight, style, locale);
	if (name != null) {
	return name;
	}

	if (id.startsWith("GMT") && id.length() > 3) {
	char sign = id.charAt(3);
	if (sign == '+' \|\| sign == '-') {
	return id;
	}
	}
	int offset = getRawOffset();
	if (daylight) {
	offset += getDSTSavings();
	}
	return ZoneInfoFile.toCustomID(offset);
	}

	private static String[] getDisplayNames(String id, Locale locale) {
	return TimeZoneNameUtility.retrieveDisplayNames(id, locale);
	}

	/**
	* Returns the amount of time to be added to local standard time
	* to get local wall clock time.
	*
	* <p>The default implementation returns 3600000 milliseconds
	* (i.e., one hour) if a call to {@link #useDaylightTime()}
	* returns {@code true}. Otherwise, 0 (zero) is returned.
	*
	* <p>If an underlying {@code TimeZone} implementation subclass
	* supports historical and future Daylight Saving Time schedule
	* changes, this method returns the amount of saving time of the
	* last known Daylight Saving Time rule that can be a future
	* prediction.
	*
	* <p>If the amount of saving time at any given time stamp is
	* required, construct a {@link Calendar} with this {@code
	* TimeZone} and the time stamp, and call {@link Calendar#get(int)
	* Calendar.get}{@code (}{@link Calendar#DST_OFFSET}{@code )}.
	*
	* @return the amount of saving time in milliseconds
	* @since 1.4
	* @see #inDaylightTime(Date)
	* @see #getOffset(long)
	* @see #getOffset(int,int,int,int,int,int)
	* @see Calendar#ZONE_OFFSET
	*/
	public int getDSTSavings() {
	if (useDaylightTime()) {
	return 3600000;
	}
	return 0;
	}

	/**
	* Queries if this {@code TimeZone} uses Daylight Saving Time.
	*
	* <p>If an underlying {@code TimeZone} implementation subclass
	* supports historical and future Daylight Saving Time schedule
	* changes, this method refers to the last known Daylight Saving Time
	* rule that can be a future prediction and may not be the same as
	* the current rule. Consider calling {@link #observesDaylightTime()}
	* if the current rule should also be taken into account.
	*
	* @return {@code true} if this {@code TimeZone} uses Daylight Saving Time,
	* {@code false}, otherwise.
	* @see #inDaylightTime(Date)
	* @see Calendar#DST_OFFSET
	*/
	public abstract boolean useDaylightTime();

	/**
	* Returns {@code true} if this {@code TimeZone} is currently in
	* Daylight Saving Time, or if a transition from Standard Time to
	* Daylight Saving Time occurs at any future time.
	*
	* <p>The default implementation returns {@code true} if
	* {@code useDaylightTime()} or {@code inDaylightTime(new Date())}
	* returns {@code true}.
	*
	* @return {@code true} if this {@code TimeZone} is currently in
	* Daylight Saving Time, or if a transition from Standard Time to
	* Daylight Saving Time occurs at any future time; {@code false}
	* otherwise.
	* @since 1.7
	* @see #useDaylightTime()
	* @see #inDaylightTime(Date)
	* @see Calendar#DST_OFFSET
	*/
	public boolean observesDaylightTime() {
	return useDaylightTime() \|\| inDaylightTime(new Date());
	}

	/**
	* Queries if the given {@code date} is in Daylight Saving Time in
	* this time zone.
	*
	* @param date the given Date.
	* @return {@code true} if the given date is in Daylight Saving Time,
	* {@code false}, otherwise.
	*/
	public abstract boolean inDaylightTime(Date date);

	/**
	* Gets the {@code TimeZone} for the given ID.
	*
	* @param ID the ID for a {@code TimeZone}, either an abbreviation
	* such as "PST", a full name such as "America/Los_Angeles", or a custom
	* ID such as "GMT-8:00". Note that the support of abbreviations is
	* for JDK 1.1.x compatibility only and full names should be used.
	*
	* @return the specified {@code TimeZone}, or the GMT zone if the given ID
	* cannot be understood.
	*/
	public static synchronized TimeZone getTimeZone(String ID) {
	return getTimeZone(ID, true);
	}

	/**
	* Gets the {@code TimeZone} for the given {@code zoneId}.
	*
	* @param zoneId a {@link ZoneId} from which the time zone ID is obtained
	* @return the specified {@code TimeZone}, or the GMT zone if the given ID
	* cannot be understood.
	* @throws NullPointerException if {@code zoneId} is {@code null}
	* @since 1.8
	*/
	public static TimeZone getTimeZone(ZoneId zoneId) {
	String tzid = zoneId.getId(); // throws an NPE if null
	char c = tzid.charAt(0);
	if (c == '+' \|\| c == '-') {
	tzid = "GMT" + tzid;
	} else if (c == 'Z' && tzid.length() == 1) {
	tzid = "UTC";
	}
	return getTimeZone(tzid, true);
	}

	/**
	* Converts this {@code TimeZone} object to a {@code ZoneId}.
	*
	* @return a {@code ZoneId} representing the same time zone as this
	* {@code TimeZone}
	* @since 1.8
	*/
	public ZoneId toZoneId() {
	ZoneId zId = zoneId;
	if (zId == null) {
	zoneId = zId = toZoneId0();
	}
	return zId;
	}

	private ZoneId toZoneId0() {
	String id = getID();
	TimeZone defaultZone = defaultTimeZone;
	// are we not defaultTimeZone but our id is equal to default's?
	if (defaultZone != this &&
	defaultZone != null && id.equals(defaultZone.getID())) {
	// delegate to default TZ which is effectively immutable
	return defaultZone.toZoneId();
	}
	// derive it ourselves
	if (ZoneInfoFile.useOldMapping() && id.length() == 3) {
	if ("EST".equals(id))
	return ZoneId.of("America/New_York");
	if ("MST".equals(id))
	return ZoneId.of("America/Denver");
	if ("HST".equals(id))
	return ZoneId.of("America/Honolulu");
	}
	return ZoneId.of(id, ZoneId.SHORT_IDS);
	}

	private static TimeZone getTimeZone(String ID, boolean fallback) {
	TimeZone tz = ZoneInfo.getTimeZone(ID);
	if (tz == null) {
	tz = parseCustomTimeZone(ID);
	if (tz == null && fallback) {
	tz = new ZoneInfo(GMT_ID, 0);
	}
	}
	return tz;
	}

	/**
	* Gets the available IDs according to the given time zone offset in milliseconds.
	*
	* @param rawOffset the given time zone GMT offset in milliseconds.
	* @return an array of IDs, where the time zone for that ID has
	* the specified GMT offset. For example, "America/Phoenix" and "America/Denver"
	* both have GMT-07:00, but differ in daylight saving behavior.
	* @see #getRawOffset()
	*/
	public static synchronized String[] getAvailableIDs(int rawOffset) {
	return ZoneInfo.getAvailableIDs(rawOffset);
	}

	/**
	* Gets all the available IDs supported.
	* @return an array of IDs.
	*/
	public static synchronized String[] getAvailableIDs() {
	return ZoneInfo.getAvailableIDs();
	}

	/**
	* Gets the platform defined TimeZone ID.
	**/
	private static native String getSystemTimeZoneID(String javaHome);

	/**
	* Gets the custom time zone ID based on the GMT offset of the
	* platform. (e.g., "GMT+08:00")
	*/
	private static native String getSystemGMTOffsetID();

	/**
	* Gets the default {@code TimeZone} of the Java virtual machine. If the
	* cached default {@code TimeZone} is available, its clone is returned.
	* Otherwise, the method takes the following steps to determine the default
	* time zone.
	*
	* <ul>
	* <li>Use the {@code user.timezone} property value as the default
	* time zone ID if it's available.</li>
	* <li>Detect the platform time zone ID. The source of the
	* platform time zone and ID mapping may vary with implementation.</li>
	* <li>Use {@code GMT} as the last resort if the given or detected
	* time zone ID is unknown.</li>
	* </ul>
	*
	* <p>The default {@code TimeZone} created from the ID is cached,
	* and its clone is returned. The {@code user.timezone} property
	* value is set to the ID upon return.
	*
	* @return the default {@code TimeZone}
	* @see #setDefault(TimeZone)
	*/
	public static TimeZone getDefault() {
	return (TimeZone) getDefaultRef().clone();
	}

	/**
	* Returns the reference to the default TimeZone object. This
	* method doesn't create a clone.
	*/
	static TimeZone getDefaultRef() {
	TimeZone defaultZone = defaultTimeZone;
	if (defaultZone == null) {
	// Need to initialize the default time zone.
	defaultZone = setDefaultZone();
	assert defaultZone != null;
	}
	// Don't clone here.
	return defaultZone;
	}

	private static synchronized TimeZone setDefaultZone() {
	TimeZone tz;
	// get the time zone ID from the system properties
	Properties props = GetPropertyAction.privilegedGetProperties();
	String zoneID = props.getProperty("user.timezone");

	// if the time zone ID is not set (yet), perform the
	// platform to Java time zone ID mapping.
	if (zoneID == null \|\| zoneID.isEmpty()) {
	String javaHome = StaticProperty.javaHome();
	try {
	zoneID = getSystemTimeZoneID(javaHome);
	if (zoneID == null) {
	zoneID = GMT_ID;
	}
	} catch (NullPointerException e) {
	zoneID = GMT_ID;
	}
	}

	// Get the time zone for zoneID. But not fall back to
	// "GMT" here.
	tz = getTimeZone(zoneID, false);

	if (tz == null) {
	// If the given zone ID is unknown in Java, try to
	// get the GMT-offset-based time zone ID,
	// a.k.a. custom time zone ID (e.g., "GMT-08:00").
	String gmtOffsetID = getSystemGMTOffsetID();
	if (gmtOffsetID != null) {
	zoneID = gmtOffsetID;
	}
	tz = getTimeZone(zoneID, true);
	}
	assert tz != null;

	final String id = zoneID;
	props.setProperty("user.timezone", id);

	defaultTimeZone = tz;
	return tz;
	}

	/**
	* Sets the {@code TimeZone} that is returned by the {@code getDefault}
	* method. {@code zone} is cached. If {@code zone} is null, the cached
	* default {@code TimeZone} is cleared. This method doesn't change the value
	* of the {@code user.timezone} property.
	*
	* @param zone the new default {@code TimeZone}, or null
	* @throws SecurityException if the security manager's {@code checkPermission}
	* denies {@code PropertyPermission("user.timezone",
	* "write")}
	* @see #getDefault
	* @see PropertyPermission
	*/
	public static void setDefault(TimeZone zone)
	{
	@SuppressWarnings("removal")
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	sm.checkPermission(new PropertyPermission
	("user.timezone", "write"));
	}
	// by saving a defensive clone and returning a clone in getDefault() too,
	// the defaultTimeZone instance is isolated from user code which makes it
	// effectively immutable. This is important to avoid races when the
	// following is evaluated in ZoneId.systemDefault():
	// TimeZone.getDefault().toZoneId().
	defaultTimeZone = (zone == null) ? null : (TimeZone) zone.clone();
	}

	/**
	* Returns true if this zone has the same rule and offset as another zone.
	* That is, if this zone differs only in ID, if at all. Returns false
	* if the other zone is null.
	* @param other the {@code TimeZone} object to be compared with
	* @return true if the other zone is not null and is the same as this one,
	* with the possible exception of the ID
	* @since 1.2
	*/
	public boolean hasSameRules(TimeZone other) {
	return other != null && getRawOffset() == other.getRawOffset() &&
	useDaylightTime() == other.useDaylightTime();
	}

	/**
	* Creates a copy of this {@code TimeZone}.
	*
	* @return a clone of this {@code TimeZone}
	*/
	public Object clone()
	{
	try {
	return super.clone();
	} catch (CloneNotSupportedException e) {
	throw new InternalError(e);
	}
	}

	/**
	* The null constant as a TimeZone.
	*/
	static final TimeZone NO_TIMEZONE = null;

	// =======================privates===============================

	/**
	* The string identifier of this {@code TimeZone}. This is a
	* programmatic identifier used internally to look up {@code TimeZone}
	* objects from the system table and also to map them to their localized
	* display names. {@code ID} values are unique in the system
	* table but may not be for dynamically created zones.
	* @serial
	*/
	private String ID;

	/**
	* Cached {@link ZoneId} for this TimeZone
	*/
	private transient ZoneId zoneId;

	private static volatile TimeZone defaultTimeZone;

	static final String GMT_ID = "GMT";
	private static final int GMT_ID_LENGTH = 3;

	/**
	* Parses a custom time zone identifier and returns a corresponding zone.
	* This method doesn't support the RFC 822 time zone format. (e.g., +hhmm)
	*
	* @param id a string of the <a href="#CustomID">custom ID form</a>.
	* @return a newly created TimeZone with the given offset and
	* no daylight saving time, or null if the id cannot be parsed.
	*/
	private static final TimeZone parseCustomTimeZone(String id) {
	int length;

	// Error if the length of id isn't long enough or id doesn't
	// start with "GMT".
	if ((length = id.length()) < (GMT_ID_LENGTH + 2) \|\|
	id.indexOf(GMT_ID) != 0) {
	return null;
	}

	ZoneInfo zi;

	// First, we try to find it in the cache with the given
	// id. Even the id is not normalized, the returned ZoneInfo
	// should have its normalized id.
	zi = ZoneInfoFile.getZoneInfo(id);
	if (zi != null) {
	return zi;
	}

	int index = GMT_ID_LENGTH;
	boolean negative = false;
	char c = id.charAt(index++);
	if (c == '-') {
	negative = true;
	} else if (c != '+') {
	return null;
	}

	int hours = 0;
	int num = 0;
	int countDelim = 0;
	int len = 0;
	while (index < length) {
	c = id.charAt(index++);
	if (c == ':') {
	if (countDelim > 0) {
	return null;
	}
	if (len > 2) {
	return null;
	}
	hours = num;
	countDelim++;
	num = 0;
	len = 0;
	continue;
	}
	if (c < '0' \|\| c > '9') {
	return null;
	}
	num = num * 10 + (c - '0');
	len++;
	}
	if (index != length) {
	return null;
	}
	if (countDelim == 0) {
	if (len <= 2) {
	hours = num;
	num = 0;
	} else {
	hours = num / 100;
	num %= 100;
	}
	} else {
	if (len != 2) {
	return null;
	}
	}
	if (hours > 23 \|\| num > 59) {
	return null;
	}
	int gmtOffset = (hours * 60 + num) * 60 * 1000;

	if (gmtOffset == 0) {
	zi = ZoneInfoFile.getZoneInfo(GMT_ID);
	if (negative) {
	zi.setID("GMT-00:00");
	} else {
	zi.setID("GMT+00:00");
	}
	} else {
	zi = ZoneInfoFile.getCustomTimeZone(id, negative ? -gmtOffset : gmtOffset);
	}
	return zi;
	}
	}

Back to index...