[cxS]

Not really 'bad' but there's just a better way of doing it.

How is it not bad? It's by pure coincidence that it's going to match the set local timezone via the MyBB UserCP, thus inaccuracy or not being synced with the time that matters kind of makes the resulting text based on it's *own* time a bit useless doesn't it? Plus you're deleting MyBB implementation to override it with some less effective javascript...

With my way of doing it, you still have MyBB functionality in-tact. It doesn't become unusable after the modification.