Member Avatar for ravi_forum

Hi ,

Is there any one help me to write the java code for displaying all compatible system time zones and setting the required time zone among those list.


Thanks and regards

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  • Latest Post Latest Post by jwenting

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As suggested, start with the Java APIs for listing and selecting time zones; the modern java.time classes (Java 8+) are recommended, with java.util.TimeZone used when a JVM-level default must be set. Practical JVM-side examples:

import java.time.ZoneId;

ZoneId.getAvailableZoneIds().stream().sorted().forEach(System.out::println);
System.out.println("Current JVM zone: " + ZoneId.systemDefault());
import java.util.TimeZone;
import java.time.ZoneId;

TimeZone.setDefault(TimeZone.getTimeZone(ZoneId.of("Europe/London")));
System.out.println("New JVM default: " + ZoneId.systemDefault());

Important limitation (echoing ): changing the JVM default does not change the operating system time zone. OS-level changes require platform tools or native calls and administrative rights. Examples: Windows has tzutil for listing/setting zones (see Microsoft docs), many Linux systems use timedatectl or updating /etc/localtime, and the canonical zone identifiers come from the IANA tz database.

Operational tips and cautions: set the JVM default early in application startup because libraries often cache the default zone; prefer IANA "Region/City" IDs (for example, "America/Los_Angeles") rather than abbreviations like "EST"; changing the default affects formatting and conversions going forward but does not alter stored epoch timestamps; mapping between Windows display names and TZ database IDs may require a lookup. For API details see the TimeZone and ZoneId Javadocs and the IANA time zone database.

References: TimeZone Javadoc, ZoneId Javadoc, tzutil (Windows), timedatectl (systemd), IANA time zones.

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Member Avatar for masijade

It would seem logical to me, to read the API doc for the TimeZone class. Doesn't that sound reasonable to you?

Member Avatar for jwenting

Java isn't designed for accessing lowlevel operating system functions like that.
You may be able to using JNI to call the required operating system functions for the operating system you have in mind, but it's better to use C (for example) for things like that.

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