Testing correct timezone handling

Java allows you to set the default timezone (java.util.TimeZone.setDefault). I've written tests before to set the timezone to a variety of different options and check that everything still works. Be careful though - if you're parallelising most of your unit tests, you'll need to make these ones sequential.

I suggest you test in some timezones with daylight saving time applies, and some without. Using an Australian timezone is good as well, as DST applies at the opposite time of the year to the northern hemisphere.

I would recommend you check out JodaTime which provides some sugar to help manage Date / Time / TimeZone type issues more legibly in your code.

We use these throughout test and production since how it boosts the native Java API for Date/Time issues is unparalleled. Using these in tests works fine within JUnit