Infinitely.
If 1 hour in World 1 is only a tiny fraction of an Earth hour, and that subsequently occurs in each new world, that means:
100 years = 876,000 hours
World 1: 1 hour = 876,000 hours (Earth)
World 2: 1 / 876,000 hours
World 3: (1 / 876,000) to the 2nd power, hours (idk how to do...