The 24-hour system is a method of expressing time, different from the 12-hour system.

In the 24-hour system, 1pm is written as 13:00 and 2pm is written as 14:00.

Although, in life, we use the 12-hour system more often. For example, we say that we get off work at 5 pm.

When we say "9 to 5", we mean 9 a.m. and 5 p.m. (the working hours of ordinary employees).

However, in scientific and rigorous explanations, in contracts and other legal documents, time should be written in 24-hour format.

The 12-hour system is a time rule that divides the 24 hours of a day into two periods, namely am (ante meridiem in Latin means before noon) and pm (post meridiem in Latin means after noon). Each period consists of twelve hours, represented by the numbers 12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 in order. The am period is from midnight to noon, and the pm period is from noon to midnight.