on my tamagotchi, My parent has a baby, and it stays with it for the rest of the day. then, it stays another day. then it goes away. i don't know of happens on other tamagotchis tho
Your adult tamagotchi must stay with it's tama baby for 2-3 nights.
They must sleep for the 2 or 3 nights otherwise the adult will remain with it's baby for longer.
Sometimes the "11:59pm" cheat dosen't always work so try setting the time to 11:29pm and wait for 31 minutes and the adult should leave. (That always works for me). <_<
Usually the parent stays one night with the baby and on the next day it wakes up at midnight and leaves few minutes later. But I have heard that in some cases, the parent has stayed longer than it should stay. I'm not sure is it normal or glitch.
Well if you pause it for a long time it stays but it took mine 2 days also for the parent to leave also(if you keep it on over night and you wake up there might possibly be 1 z then turn on its light and theres might be a baby sleeping)