AM and PM Explained

The 12-hour system divides the 24 hours of a day into two periods lasting 12 hours each. The first 12-hour period is designated as am. It runs from midnight to noon. The second period, marked pm, covers the 12 hours from noon to midnight.

The abbreviations am and pm derive from Latin:

• AM = Ante meridiem: Before noon
• PM = Post meridiem: After noon

Using numbers from 1 to 12, followed by am or pm, the 12-hour clock system identifies all 24 hours of the day. For example, 5 am is early in the morning, and 5 pm is late in the afternoon; 1 am is one hour after midnight, while 11 pm is one hour before midnight

Ante meridiem is commonly denoted as AM, am, a.m., or A.M.; post meridiem is usually abbreviated PM, pm, p.m., or P.M.