Yes, 12 am and midnight mean the same thing and can be used interchangeably. They both represent the start of the day, which is midnight, and can refer to the same time. 12 am is the start of a new day, noon is the halfway point, and 12 pm is the end of the day.
A full 24-hour day consists of 24 hours, starting at 12 am (midnight) and ending at 11:59 pm. Therefore, 12 am and midnight both refer to the start of a new day.
