TimeZone represents a time zone offset, and also figures out daylight
* savings.
*
*
* Typically, you get a TimeZone using getDefault
* which creates a TimeZone based on the time zone where the program
* is running. For example, for a program running in Japan, getDefault
* creates a TimeZone object based on Japanese Standard Time.
*
*
* You can also get a TimeZone using 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 TimeZone object with:
*
* TimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
* getAvailableIDs method to iterate through
* all the supported time zone IDs. You can then choose a
* supported ID to get a 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:
*
* * * Hours must be between 0 to 23 and Minutes must be * between 00 to 59. For example, "GMT+10" and "GMT+0010" mean ten * hours and ten minutes ahead of GMT, respectively. ** CustomID: *GMTSign Hours:Minutes *GMTSign Hours Minutes *GMTSign Hours * Sign: one of *+ -* Hours: * Digit * Digit Digit * Minutes: * Digit Digit * Digit: one of *0 1 2 3 4 5 6 7 8 9*
* 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, "GMT"
* is used.
*
* When creating a TimeZone, the specified custom time
* zone ID is normalized in the following syntax:
*
* For example, TimeZone.getTimeZone("GMT-8").getID() returns "GMT-08:00". * ** NormalizedCustomID: *GMTSign TwoDigitHours:Minutes * Sign: one of *+ -* TwoDigitHours: * Digit Digit * Minutes: * Digit Digit * Digit: one of *0 1 2 3 4 5 6 7 8 9*
getDisplayName() indicating
* a short name, such as "PST."
* @see #LONG
* @since 1.2
*/
public static final int SHORT = 0;
/**
* A style specifier for 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
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.
*
* This method returns a historically correct offset if an
* underlying 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 standard
* 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.
*
* 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. *
* If an underlying 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.
*/
abstract public 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 raw
* offset.
*
* If an underlying 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.
*
*
This method is equivalent to: *
* getDisplayName(false, {@link #LONG},
* Locale.getDefault({@link Locale.Category#DISPLAY}))
* This method is equivalent to: *
* getDisplayName(false, {@link #LONG}, locale)
* This method is equivalent to: *
* getDisplayName(daylight, style,
* Locale.getDefault({@link Locale.Category#DISPLAY}))
* When looking up a time zone name, the {@linkplain
* ResourceBundle.Control#getCandidateLocales(String,Locale) default
* Locale search path of ResourceBundle} derived
* from the specified {@code locale} is used. (No {@linkplain
* ResourceBundle.Control#getFallbackLocale(String,Locale) fallback
* 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
* normalized custom ID format 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.
* @exception IllegalArgumentException if {@code style} is invalid.
* @exception 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.
*
*
The default implementation returns 3600000 milliseconds * (i.e., one hour) if a call to {@link #useDaylightTime()} * returns {@code true}. Otherwise, 0 (zero) is returned. * *
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. * *
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. * *
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. * *
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.
*/
abstract public boolean inDaylightTime(Date date);
/**
* Gets the TimeZone for the given ID.
*
* @param ID the ID for a 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 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.
*
*
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
String zoneID = AccessController.doPrivileged(
new GetPropertyAction("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 = AccessController.doPrivileged(
new GetPropertyAction("java.home"));
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;
AccessController.doPrivileged(new PrivilegedAction<>() {
@Override
public Void run() {
System.setProperty("user.timezone", id);
return null;
}
});
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)
{
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 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 TimeZone.
*
* @return a clone of this 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 TimeZone. This is a
* programmatic identifier used internally to look up TimeZone
* objects from the system table and also to map them to their localized
* display names. 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;
// a static TimeZone we can reference if no AppContext is in place
private static volatile TimeZone mainAppContextDefault;
/**
* 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 custom ID form.
* @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;
}
}