The earliest I have had one to break the shell was mid day 17. He hatched on day 18 late. But I have had one hatch on day 18 early. If that doesn't count just let me know. Thanks
All 5 of mine hatched on day 19. It was really hot here though-- I have one more broody "due" soon, and I'll be expecting hers around day 18 or 19 because it's even hotter.