No, this isn't a duplicate of all the normal "make badges and the rep cap day local" requests. It's very specific to April 1st.
Users should be required to specify their time zone next time they log in to Stack Overflow:
- Don't present a list; lazy users will just pick a random entry
- Insist on both the Windows system ID for the time zone and the Olsen database name. That way there's no room for ambiguity.
- If a user can't get a valid combination after 3 attempts, suspend them. They're clearly not trying hard enough.
- Allow a user to change their time zone only when the date of their current time zone is the same as the date within the new time zone.
- Periodically confirm their time zone by giving them pop quiz on when their DST will next change (if at all).
Then, and only then, can we make sure that any April Fool's Day specific features show up at the right time.