There is also another type rollover advance during regular playtime, each time doing +1.
I'd be RNGing something in HGSS without calls/radio, and I'd use the NPCs and walking to advance the frame. Instead of walking I would "time warp" to another time, usually +1 hour did the trick. I would then advance 1 frame. Repeatable, and it didn't work when going back in time obviously. Mind you this was on an emulator, I'm too lazy to wait on a DS :) Never figured out what triggered it (never debugged).