Thanks guys!
It's basically example code "RTC" from Time library examples.
RTC.set(now()); sounds like what I'm looking for, thanks Jack!
arghduino, I've tried Ada's example before, it doesn't set my RTC's chip time for some reason. I posted on adafruit forum, and they say it's because I'm not using their kit, which is true, but I don't see how it matters since I'm using same DS1307 chip.