Definition
Midnight
Midnight is the instant when one calendar day ends and the next begins.
What it means
Midnight is the join between two dates. 00:00 Monday is the very start of Monday, immediately after 23:59 Sunday.
Remember it
Midnight is the doorway into the next date.
Example
A train leaves at 23:50 on Friday and arrives at 00:20 on Saturday. It travels 10 minutes to midnight and 20 minutes after, so the duration is 30 minutes.
Watch for
Midnight is not the daytime twelve; noon is 12 o’clock during the day.
Common mix-up
The phrase “midnight on Monday” can be unclear. Use a date and 00:00, such as 00:00 Monday, when precision matters.
Exact meaning
Midnight is the boundary between two calendar dates. In 24-hour time, 00:00 is the start of the named date. Adding the date avoids ambiguity, and writing “midnight” is clearer than writing 12 a.m. or 12 p.m.