TimeZone represents a time zone offset, and also computes 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(String) 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");

You can use the getAvailableIDs() method to iterate through all the supported time zone IDs, or getCanonicalID method to check if a time zone ID is supported or not. 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 you can create a custom time zone ID with the following syntax:

GMT[+|-]hh[[:]mm]

For example, you might specify GMT+14:00 as a custom time zone ID. The TimeZone that is returned when you specify a custom time zone ID uses the specified offset from GMT(=UTC) and does not observe daylight saving time. For example, you might specify GMT+14:00 as a custom time zone ID to create a TimeZone representing 14 hours ahead of GMT (with no daylight saving time). In addition, getCanonicalID can also be used to normalize a custom time zone ID.

For compatibility with JDK 1.1.x, some other three-letter time zone IDs (such as "PST", "CTT", "AST") are also supported. However, their use is deprecated 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.

#
# The default TimeZone implementation type used by the ICU TimeZone
# factory method. [ ICU | JDK ]
#
com.ibm.icu.util.TimeZone.DefaultTimeZoneType = ICU

This property is included in ICUConfig.properties in com.ibm.icu package. When the TimeZone class is loaded, the initialization code checks if the property com.ibm.icu.util.TimeZone.DefaultTimeZoneType=xxx is defined by the system properties. If not available, then it loads ICUConfig.properties to get the default time zone implementation type. The property setting is only used for the initial default value and you can change the default type by calling setDefaultTimeZoneType at runtime.