Most game worlds have 20 minute days, a few have 15 minute game days. And each game-month has 24 game-days (don't ask why). So in a 20 minute / day world, it works likes this:
1 game day = 20 minutes
3 game days = 1 hour
1 month (24 game days) = 8 hours
1 year = 96 hours (4 days)
30 years = 120 days (about 4 months) IRL
Game worlds are re-set at the end of their timeline manually by the developer (as far as we know). Sometimes a game world will be allowed to go a little overtime if another world is nearing it's end, then both will be re-set together (the latter one can end early in this case).
Game worlds will therefore generally re-set at the END of the final year, +/- about 6 game-months either early or late. It's not an exact science.