org.joda.time
Class DateTimeZone

java.lang.Object
  org.joda.time.DateTimeZone

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

CachedDateTimeZone, FixedDateTimeZone

public abstract class DateTimeZone
extends Object
implements Serializable

DateTimeZone represents a time zone.

A time zone is a system of rules to convert time from one geographic location to another. For example, Paris, France is one hour ahead of London, England. Thus when it is 10:00 in London, it is 11:00 in Paris.

All time zone rules are expressed, for historical reasons, relative to Greenwich, London. Local time in Greenwich is referred to as Greenwich Mean Time (GMT). This is similar, but not precisely identical, to Universal Coordinated Time, or UTC. This library only uses the term UTC.

Using this system, America/Los_Angeles is expressed as UTC-08:00, or UTC-07:00 in the summer. The offset -08:00 indicates that America/Los_Angeles time is obtained from UTC by adding -08:00, that is, by subtracting 8 hours.

The offset differs in the summer because of daylight saving time, or DST. The following definitions of time are generally used:

• UTC - The reference time.
• Standard Time - The local time without a daylight saving time offset. For example, in Paris, standard time is UTC+01:00.
• Daylight Saving Time - The local time with a daylight saving time offset. This offset is typically one hour, but not always. It is typically used in most countries away from the equator. In Paris, daylight saving time is UTC+02:00.
• Wall Time - This is what a local clock on the wall reads. This will be either Standard Time or Daylight Saving Time depending on the time of year and whether the location uses Daylight Saving Time.

Unlike the Java TimeZone class, DateTimeZone is immutable. It also only supports long format time zone ids. Thus EST and ECT are not accepted. However, the factory that accepts a TimeZone will attempt to convert from the old short id to a suitable long id.

There are four approaches to loading time-zone data, which are tried in this order:

1. load the specific Provider specified by the system property org.joda.time.DateTimeZone.Provider.
2. load ZoneInfoProvider using the data in the filing system folder pointed to by system property org.joda.time.DateTimeZone.Folder.
3. load ZoneInfoProvider using the data in the classpath location org/joda/time/tz/data.
4. load UTCProvider

Unless you override the standard behaviour, the default if the third approach.

DateTimeZone is thread-safe and immutable, and all subclasses must be as well.

Since:

1.0

See Also:

Serialized Form

UTC

public static final DateTimeZone UTC

The time zone for Universal Coordinated Time

DateTimeZone

protected DateTimeZone(String id)

Constructor.

Parameters:

id - the id to use

Throws:

IllegalArgumentException - if the id is null

getDefault

public static DateTimeZone getDefault()

Gets the default time zone.

The default time zone is derived from the system property user.timezone. If that is null or is not a valid identifier, then the value of the JDK TimeZone default is converted. If that fails, UTC is used.

NOTE: If the java.util.TimeZone default is updated after calling this method, then the change will not be picked up here.

Returns:

the default datetime zone object

setDefault

public static void setDefault(DateTimeZone zone)
                       throws SecurityException

Sets the default time zone.

NOTE: Calling this method does not set the java.util.TimeZone default.

Parameters:

zone - the default datetime zone object, must not be null

Throws:

IllegalArgumentException - if the zone is null

SecurityException - if the application has insufficient security rights

forID

public static DateTimeZone forID(String id)

Gets a time zone instance for the specified time zone id.

The time zone id may be one of those returned by getAvailableIDs. Short ids, as accepted by TimeZone, are not accepted. All IDs must be specified in the long format. The exception is UTC, which is an acceptable id.

Alternatively a locale independent, fixed offset, datetime zone can be specified. The form [+-]hh:mm can be used.

Parameters:

id - the ID of the datetime zone, null means default

Returns:

the DateTimeZone object for the ID

Throws:

IllegalArgumentException - if the ID is not recognised

forOffsetHours

public static DateTimeZone forOffsetHours(int hoursOffset)
                                   throws IllegalArgumentException

Gets a time zone instance for the specified offset to UTC in hours. This method assumes standard length hours.

This factory is a convenient way of constructing zones with a fixed offset.

Parameters:

hoursOffset - the offset in hours from UTC, from -23 to +23

Returns:

the DateTimeZone object for the offset

Throws:

IllegalArgumentException - if the offset is too large or too small

forOffsetHoursMinutes

public static DateTimeZone forOffsetHoursMinutes(int hoursOffset,
                                                 int minutesOffset)
                                          throws IllegalArgumentException

Gets a time zone instance for the specified offset to UTC in hours and minutes. This method assumes 60 minutes in an hour, and standard length minutes.

This factory is a convenient way of constructing zones with a fixed offset. The hours value must be in the range -23 to +23. The minutes value must be in the range -59 to +59. The following combinations of sign for the hour and minute are possible:

  Hour    Minute    Example    Result
 
  +ve     +ve       (2, 15)    +02:15
  +ve     zero      (2, 0)     +02:00
  +ve     -ve       (2, -15)   IllegalArgumentException
 
  zero    +ve       (0, 15)    +00:15
  zero    zero      (0, 0)     +00:00
  zero    -ve       (0, -15)   -00:15
 
  -ve     +ve       (-2, 15)   -02:15
  -ve     zero      (-2, 0)    -02:00
  -ve     -ve       (-2, -15)  -02:15
 

Note that in versions before 2.3, the minutes had to be zero or positive.

Parameters:

hoursOffset - the offset in hours from UTC, from -23 to +23

minutesOffset - the offset in minutes from UTC, from -59 to +59

Returns:

the DateTimeZone object for the offset

Throws:

IllegalArgumentException - if any value is out of range, the minutes are negative when the hours are positive, or the resulting offset exceeds +/- 23:59:59.000

forOffsetMillis

public static DateTimeZone forOffsetMillis(int millisOffset)

Gets a time zone instance for the specified offset to UTC in milliseconds.

Parameters:

millisOffset - the offset in millis from UTC, from -23:59:59.999 to +23:59:59.999

Returns:

the DateTimeZone object for the offset

forTimeZone

public static DateTimeZone forTimeZone(TimeZone zone)

Gets a time zone instance for a JDK TimeZone.

DateTimeZone only accepts a subset of the IDs from TimeZone. The excluded IDs are the short three letter form (except UTC). This method will attempt to convert between time zones created using the short IDs and the full version.

This method is not designed to parse time zones with rules created by applications using SimpleTimeZone directly.

Parameters:

zone - the zone to convert, null means default

Returns:

the DateTimeZone object for the zone

Throws:

IllegalArgumentException - if the zone is not recognised

getAvailableIDs

public static Set<String> getAvailableIDs()

Gets all the available IDs supported.

Returns:

an unmodifiable Set of String IDs

getProvider

public static Provider getProvider()

Gets the zone provider factory.

The zone provider is a pluggable instance factory that supplies the actual instances of DateTimeZone.

Returns:

the provider

setProvider

public static void setProvider(Provider provider)
                        throws SecurityException

Sets the zone provider factory.

The zone provider is a pluggable instance factory that supplies the actual instances of DateTimeZone.

Parameters:

provider - provider to use, or null for default

Throws:

SecurityException - if you do not have the permission DateTimeZone.setProvider

IllegalArgumentException - if the provider is invalid

getNameProvider

public static NameProvider getNameProvider()

Gets the name provider factory.

The name provider is a pluggable instance factory that supplies the names of each DateTimeZone.

Returns:

the provider

setNameProvider

public static void setNameProvider(NameProvider nameProvider)
                            throws SecurityException

Sets the name provider factory.

The name provider is a pluggable instance factory that supplies the names of each DateTimeZone.

Parameters:

nameProvider - provider to use, or null for default

Throws:

SecurityException - if you do not have the permission DateTimeZone.setNameProvider

IllegalArgumentException - if the provider is invalid

getID

public final String getID()

Gets the ID of this datetime zone.

Returns:

the ID of this datetime zone

getNameKey

public abstract String getNameKey(long instant)

Returns a non-localized name that is unique to this time zone. It can be combined with id to form a unique key for fetching localized names.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the name for

Returns:

name key or null if id should be used for names

getShortName

public final String getShortName(long instant)

Gets the short name of this datetime zone suitable for display using the default locale.

If the name is not available for the locale, then this method returns a string in the format [+-]hh:mm.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the name for

Returns:

the human-readable short name in the default locale

getShortName

public String getShortName(long instant,
                           Locale locale)

Gets the short name of this datetime zone suitable for display using the specified locale.

If the name is not available for the locale, then this method returns a string in the format [+-]hh:mm.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the name for

locale - the locale to get the name for

Returns:

the human-readable short name in the specified locale

getName

public final String getName(long instant)

Gets the long name of this datetime zone suitable for display using the default locale.

If the name is not available for the locale, then this method returns a string in the format [+-]hh:mm.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the name for

Returns:

the human-readable long name in the default locale

getName

public String getName(long instant,
                      Locale locale)

Gets the long name of this datetime zone suitable for display using the specified locale.

If the name is not available for the locale, then this method returns a string in the format [+-]hh:mm.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the name for

locale - the locale to get the name for

Returns:

the human-readable long name in the specified locale

getOffset

public abstract int getOffset(long instant)

Gets the millisecond offset to add to UTC to get local time.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the offset for

Returns:

the millisecond offset to add to UTC to get local time

getOffset

public final int getOffset(ReadableInstant instant)

Gets the millisecond offset to add to UTC to get local time.

Parameters:

instant - instant to get the offset for, null means now

Returns:

the millisecond offset to add to UTC to get local time

getStandardOffset

public abstract int getStandardOffset(long instant)

Gets the standard millisecond offset to add to UTC to get local time, when standard time is in effect.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the offset for

Returns:

the millisecond offset to add to UTC to get local time

isStandardOffset

public boolean isStandardOffset(long instant)

Checks whether, at a particular instant, the offset is standard or not.

This method can be used to determine whether Summer Time (DST) applies. As a general rule, if the offset at the specified instant is standard, then either Winter time applies, or there is no Summer Time. If the instant is not standard, then Summer Time applies.

The implementation of the method is simply whether getOffset(long) equals getStandardOffset(long) at the specified instant.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z to get the offset for

Returns:

true if the offset at the given instant is the standard offset

Since:

1.5

getOffsetFromLocal

public int getOffsetFromLocal(long instantLocal)

Gets the millisecond offset to subtract from local time to get UTC time. This offset can be used to undo adding the offset obtained by getOffset.

 millisLocal == millisUTC   + getOffset(millisUTC)
 millisUTC   == millisLocal - getOffsetFromLocal(millisLocal)
 

NOTE: After calculating millisLocal, some error may be introduced. At offset transitions (due to DST or other historical changes), ranges of local times may map to different UTC times.

For overlaps (where the local time is ambiguous), this method returns the offset applicable before the gap. The effect of this is that any instant calculated using the offset from an overlap will be in "summer" time.

For gaps, this method returns the offset applicable before the gap, ie "winter" offset. However, the effect of this is that any instant calculated using the offset from a gap will be after the gap, in "summer" time.

For example, consider a zone with a gap from 01:00 to 01:59:
Input: 00:00 (before gap) Output: Offset applicable before gap DateTime: 00:00
Input: 00:30 (before gap) Output: Offset applicable before gap DateTime: 00:30
Input: 01:00 (in gap) Output: Offset applicable before gap DateTime: 02:00
Input: 01:30 (in gap) Output: Offset applicable before gap DateTime: 02:30
Input: 02:00 (after gap) Output: Offset applicable after gap DateTime: 02:00
Input: 02:30 (after gap) Output: Offset applicable after gap DateTime: 02:30

NOTE: Prior to v2.0, the DST overlap behaviour was not defined and varied by hemisphere. Prior to v1.5, the DST gap behaviour was also not defined. In v2.4, the documentation was clarified again.

Parameters:

instantLocal - the millisecond instant, relative to this time zone, to get the offset for

Returns:

the millisecond offset to subtract from local time to get UTC time

convertUTCToLocal

public long convertUTCToLocal(long instantUTC)

Converts a standard UTC instant to a local instant with the same local time. This conversion is used before performing a calculation so that the calculation can be done using a simple local zone.

Parameters:

instantUTC - the UTC instant to convert to local

Returns:

the local instant with the same local time

Throws:

ArithmeticException - if the result overflows a long

Since:

1.5

convertLocalToUTC

public long convertLocalToUTC(long instantLocal,
                              boolean strict,
                              long originalInstantUTC)

Converts a local instant to a standard UTC instant with the same local time attempting to use the same offset as the original.

This conversion is used after performing a calculation where the calculation was done using a simple local zone. Whenever possible, the same offset as the original offset will be used. This is most significant during a daylight savings overlap.

Parameters:

instantLocal - the local instant to convert to UTC

strict - whether the conversion should reject non-existent local times

originalInstantUTC - the original instant that the calculation is based on

Returns:

the UTC instant with the same local time,

Throws:

ArithmeticException - if the result overflows a long

IllegalArgumentException - if the zone has no equivalent local time

Since:

2.0

convertLocalToUTC

public long convertLocalToUTC(long instantLocal,
                              boolean strict)

Converts a local instant to a standard UTC instant with the same local time. This conversion is used after performing a calculation where the calculation was done using a simple local zone.

Parameters:

instantLocal - the local instant to convert to UTC

strict - whether the conversion should reject non-existent local times

Returns:

the UTC instant with the same local time,

Throws:

ArithmeticException - if the result overflows a long

IllegalInstantException - if the zone has no equivalent local time

Since:

1.5

getMillisKeepLocal

public long getMillisKeepLocal(DateTimeZone newZone,
                               long oldInstant)

Gets the millisecond instant in another zone keeping the same local time.

The conversion is performed by converting the specified UTC millis to local millis in this zone, then converting back to UTC millis in the new zone.

Parameters:

newZone - the new zone, null means default

oldInstant - the UTC millisecond instant to convert

Returns:

the UTC millisecond instant with the same local time in the new zone

isLocalDateTimeGap

public boolean isLocalDateTimeGap(LocalDateTime localDateTime)

Checks if the given LocalDateTime is within a gap.

When switching from standard time to Daylight Savings Time there is typically a gap where a clock hour is missing. This method identifies whether the local datetime refers to such a gap.

Parameters:

localDateTime - the time to check, not null

Returns:

true if the given datetime refers to a gap

Since:

1.6

adjustOffset

public long adjustOffset(long instant,
                         boolean earlierOrLater)

Adjusts the offset to be the earlier or later one during an overlap.

Parameters:

instant - the instant to adjust

earlierOrLater - false for earlier, true for later

Returns:

the adjusted instant millis

isFixed

public abstract boolean isFixed()

Returns true if this time zone has no transitions.

Returns:

true if no transitions

nextTransition

public abstract long nextTransition(long instant)

Advances the given instant to where the time zone offset or name changes. If the instant returned is exactly the same as passed in, then no changes occur after the given instant.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z

Returns:

milliseconds from 1970-01-01T00:00:00Z

previousTransition

public abstract long previousTransition(long instant)

Retreats the given instant to where the time zone offset or name changes. If the instant returned is exactly the same as passed in, then no changes occur before the given instant.

Parameters:

instant - milliseconds from 1970-01-01T00:00:00Z

Returns:

milliseconds from 1970-01-01T00:00:00Z

toTimeZone

public TimeZone toTimeZone()

Get the datetime zone as a TimeZone.

Returns:

the closest matching TimeZone object

equals

public abstract boolean equals(Object object)

Compare this datetime zone with another.

Overrides:

equals in class Object

Parameters:

object - the object to compare with

Returns:

true if equal, based on the ID and all internal rules

hashCode

public int hashCode()

Gets a hash code compatable with equals.

Overrides:

hashCode in class Object

Returns:

suitable hashcode

toString

public String toString()

Gets the datetime zone as a string, which is simply its ID.

Overrides:

toString in class Object

Returns:

the id of the zone

writeReplace

protected Object writeReplace()
                       throws ObjectStreamException

By default, when DateTimeZones are serialized, only a "stub" object referring to the id is written out. When the stub is read in, it replaces itself with a DateTimeZone object.

Returns:

a stub object to go in the stream

Throws:

ObjectStreamException