New Year’s Eve ends and New Year’s Day begins at midnight on the standard civil calendar.
Midnight is the boundary between one calendar date and the next. In the usual 24-hour convention, it is written as 00:00 at the start of the new day, while 24:00 can be used to describe the end of the preceding day in some technical contexts.
Public celebrations often count down to this instant, when local clocks reach 12:00 at night. Because the world is divided into time zones, midnight arrives at different moments around the globe rather than simultaneously everywhere.
The phrase “12 a.m.” can cause confusion because some people use it for the beginning of a day and others avoid it. A digital clock showing 00:00 removes that ambiguity. The civil-calendar transition is also distinct from astronomical events such as the exact moment of a solstice or the Earth’s position in orbit.