Minecraft wiki entry for Turtle_Egg, associated text: Turtle eggs have a very low chance of cracking during random ticks during the day (1/500 chance). However, they are almost guaranteed to crack during random ticks between 21600 and 22550 ticks in-game time (3:36 am and 4:33 am). This is a roughly 48-second window for the player. About 95% of eggs crack or hatch during this night-time window. On average, an egg hatches in 4-5 nights. 90% of eggs hatch in 7 nights or less.[2]