12 AM, also known as midnight, marks the transition from one day to the next. It is the point when the clock strikes twelve, indicating the end of the current day and the beginning of a new one. In a 12-hour clock system, 12 AM is the first hour of the day, while in a 24-hour clock, it is represented as 00:00. Midnight is significant in various cultures and contexts. For example, it is often associated with the start of celebrations, such as New Year's Eve, when people welcome the new year. Additionally, many businesses and services operate on a 24-hour schedule, making midnight an important reference point for closing and opening times.