I just been bugged by the Day light saving hours I seem that 3rd November 2013 01:00:00 start EST time Now ever Time I set my time to 3rd November 2013 00:58:xx(some seconds) and run date it give me valid Time zone i.e EDT but even after the time pass 01:00:00 and I still query the date library I still see the Time zone as EDT and not EST have a look at this screenshot You can clearly see the Time zone saying as EDT even when it is EST any one has a clue for this Update There is one other finding I found if I restart my machine I see this