The very most difficult part of writing date and time handling code is interfacing with systems whose developer thought date and time handling was completely straightforward :P.
It's hard, but it's not that hard so long as all the data is there. The biggest difficulty is working out the right frame of reference to store timestamps with. That's mostly only a catastrophic problem for future events involving people, but (as others in the thread note) it's still potentially an issue for audit (and other) data too.
Knowing which time zone a meeting is supposed to be held in is especially important around time zone changes.
It's hard, but it's not that hard so long as all the data is there. The biggest difficulty is working out the right frame of reference to store timestamps with. That's mostly only a catastrophic problem for future events involving people, but (as others in the thread note) it's still potentially an issue for audit (and other) data too.
Knowing which time zone a meeting is supposed to be held in is especially important around time zone changes.