Question

I’m looking for a better way to set Java’s default timezone. We’re currently hitting our DB2 database to get it’s current timezone, but it’s not a timezone name, just the current hours/minutes offset value. So we take that value and construct an ID like “GMT-07:00”.

That seems to cause two problems:

1. We have to make sure to reset for DST start/end. e.g. we have set up a scheduled task the queries the database and sets the timezone. Annoying.
2. For reasons unknown to us (yet), our scheduled task will SOMETIMES set the wrong timezone.

Assuming that DB2 always returns the correct value then I can only imagine that “GMT-07:00” is vague and between Java/it’s timezone db/the OS, it plucks a different value from the table.

After computing a string like “GMT-07:00” our code does this:

 String timezoneGMTOffsetString = "GMT-07:00";
 TimeZone localTimeZone = TimeZone.getTimeZone(timezoneGMTOffsetString);
 TimeZone.setDefault(localTimeZone);
 System.setProperty("user.timezone", timezoneGMTOffsetString);

We think we’re just going to have to set the value externally and use -Duser.timezone="America/Los_Angeles" when starting Tomcat. And then we can scrap the scheduled job!

Any advice? Java 6.0_26

Answer 1

The preferred solution is always covert to UTC and from UTC. Use joda-time library for conversion.