[obtu]

You missed one of his requirements, which is he wants be able to compute "three months after" on the dates he stores, which is a timezone-sensitive calculation. This sort of requirement is commonly found in calendaring. That means he does need to store symbolic information for each date or datetime stored.

[sicxu]

You need timezone for sure. You just don't have to store it along with every date/time value. You can store it as user preference for example. What if you are scheduling a meeting between a U.S developer and an India developer?

[obtu]

The date of the meeting mustn't depend on the display preferences of one of the participants. The meeting itself has to be anchored to a time zone.