The time period "00:00 - 00:01" is midnight. On computer clocks, the day changes to the next day the minute(s) after midnight.
Start and end of day[change | change source]
In the world, midnight is the start of one day and the end of the last day. It's the dividing point between two days.
In the United States and Canada, digital clocks and computers usually show 12 a.m. right at midnight. However, people have to remember that any time is actually an instant. The "a.m." shown on clock displays means the 12-hour period after the instant of midnight. So when a clock says "12:00 a.m.", midnight has already passed and a new day has started. In other words, 11:59 p.m. shows until midnight; at the instant of midnight, it changes to 12:00. At the same time, the p.m. changes to a.m., but a.m. does not mean the instant of midnight which separates p.m. and a.m.
At 24-hour system[change | change source]
Midnight is also 0 o'clock but 0 o'clock in 24-hour system
23:59 24:00 00:00