Determine Whether Daylight Savings Time (DST) is Active in Java for a Specified Date

Question

I have a Java class that takes in the latitude/longitude of a location and returns the GMT offset when daylight savings time is on and off. I am looking for an easy way to

Answer 1

This is the answer for the machine on which the question is being asked:

TimeZone.getDefault().inDaylightTime( new Date() );

A server trying to figure this out for a client will need the client's time zone. See @Powerlord answer for the reason why.

For any particular TimeZone

TimeZone.getTimeZone( "US/Alaska").inDaylightTime( new Date() );