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

Joda Time contains handling methods which will calculate the offsets for you. See DateTimeZone.convertLocalToUTC(...)

To supplement this, you will need to look up the current time zone with your latitude/longitude info. GeoNames provides a java client for its web service, as well as a simple web-request framework (i.e. http://ws.geonames.org/timezone?lat=47.01&lng=10.2)