If you change the time then the age counter sometimes freezes temporarily, which may affect your Tamagotchi's growth. If anything, it will slow the growth down. Example: You have a 0-year-old toddler Music Star. You are planning to leave it on overnight so it will evolve in the morning. However, you notice that the clock says 8:30, however your Tama says 8:15. You change the time on your Tama to 8:30. Next morning, there is a 50% chance the Tama will not evolve.