I just got this game, but it's pretty similar to AC for the DS. Some things* you can only find or do at night.
- *Fish for the rare night stuff
- *Look around for rare night bugs on trees or crawling around (if a tarantula or scorpion is nearby, you'll hear this weird sound - careful, they bite)
- Look for the Money Rock with a shovel
- Visit animal neighbors who are up and they send you on errands and give gifts (sometimes you have to talk to them more than once to get this)
- Letter-writing (with a gift inserted) to neighbors to get letter gifts from them in the morning
- *Saturdays, 8pm-12am, go to the Coffee Shop and get songs from KK to play in your [music furniture] like a radio, turntable, etc
- Shake trees for bags of bells or furniture (but watch out for beehives)
- *8pm or later, meet Wisp the Ghost and he gives you 1 wish out of 3 choices