Google already has an April prank posted as a fake new Gmail feature, even though it's still March 31st:
http://mail.google.com/mail/help/customtime/index.html
Oh Google, you can do better than that...
(Don't mind the time stamp on this entry, for all entries are posted on Japan time)
I got fooled! I totally thought that was a strange new feature and wondered how much chaos could ensue from "Custom Time". BTW, Happy BD, Adam!