After 24 hours, change the time to 11:59pm and wait one minute. The parent should get out of bed and gaze down on the baby. After a few miutes, the parent should leave the baby and this will be your 2nd Generation of Tamagotchi.
Ok, before you try this, make sure that it has been 1 night after the baby was born.
Ok, set the time to 11:59PM and wait one minute, if you would like to view what happens, don't turn the lights out. While the process of the parent leaving is in progress, you cannot do anything until it's over.
Remember, this won't always work the first time. Just keep trying, and make sure the baby has been with it's parent for 24 hours of no pausing, otherwise, it won't work at all.