AM and PM — What Do They Stand For?
AM stands for Ante Meridiem (Latin for ‘before midday’) and covers 12:00 midnight to 11:59 in the morning. PM stands for Post Meridiem (‘after midday’) and covers 12:00 noon to 11:59 at night. Together they divide the 24-hour day into two 12-hour halves.
Quick Answer
AM — Ante Meridiem
12:00 AM – 11:59 AM
Midnight through late morning. Starts at 00:00 in 24-hour time.
PM — Post Meridiem
12:00 PM – 11:59 PM
Noon through late night. Starts at 12:00 in 24-hour time.
AM vs PM — Full Comparison
| AM | PM | |
|---|---|---|
| Full name | Ante Meridiem | Post Meridiem |
| Meaning | Before midday | After midday |
| Time range | 12:00 AM – 11:59 AM | 12:00 PM – 11:59 PM |
| 24-hour equivalent | 00:00 – 11:59 | 12:00 – 23:59 |
| Example | 9:00 AM = morning | 9:00 PM = evening |
12-Hour to 24-Hour Conversion Chart
The table below shows every hour of the day in both 12-hour AM/PM format and 24-hour (military) format.
| 12-Hour | 24-Hour | Period |
|---|---|---|
| 12:00 AM (midnight) | 00:00 | AM |
| 1:00 AM | 01:00 | AM |
| 2:00 AM | 02:00 | AM |
| 3:00 AM | 03:00 | AM |
| 4:00 AM | 04:00 | AM |
| 5:00 AM | 05:00 | AM |
| 6:00 AM | 06:00 | AM |
| 7:00 AM | 07:00 | AM |
| 8:00 AM | 08:00 | AM |
| 9:00 AM | 09:00 | AM |
| 10:00 AM | 10:00 | AM |
| 11:00 AM | 11:00 | AM |
| 12:00 PM (noon) | 12:00 | PM |
| 1:00 PM | 13:00 | PM |
| 2:00 PM | 14:00 | PM |
| 3:00 PM | 15:00 | PM |
| 4:00 PM | 16:00 | PM |
| 5:00 PM | 17:00 | PM |
| 6:00 PM | 18:00 | PM |
| 7:00 PM | 19:00 | PM |
| 8:00 PM | 20:00 | PM |
| 9:00 PM | 21:00 | PM |
| 10:00 PM | 22:00 | PM |
| 11:00 PM | 23:00 | PM |
Rows highlighted in amber mark the two special cases: 12:00 AM (midnight) and 12:00 PM (noon).
The Confusing Part: Is 12 AM Midnight or Noon?
12:00 AM is midnight. 12:00 PM is noon. This is the most confusing part of the 12-hour system. Think of it this way: 12:01 AM is just after midnight (early morning), so 12:00 AM must be midnight. 12:01 PM is just after noon, so 12:00 PM must be noon.
12 AM
Midnight
= 00:00
Start of the new calendar day. The darkest part of the night.
12 PM
Noon
= 12:00
The middle of the day. The Sun is at its highest point.
Which Countries Use AM/PM?
The 12-hour AM/PM system is primarily used in:
- United States
- Canada
- Australia
- Philippines
- Malaysia
- India
- Pakistan
- Bangladesh
- Egypt
- Saudi Arabia
- Colombia
- Mexico
Most of Europe, East Asia, and Latin America use the 24-hour clock. For example, 3 PM in Germany is written as 15:00, not 3 PM.
How to Remember AM vs PM
The Latin origins are the most reliable guide, but two simple mnemonics also work well:
AM = “After Midnight”
Not technically correct, but it works as a memory hook. AM hours run from midnight through the morning.
PM = “Past Midday”
PM hours begin at noon and run through the rest of the day until just before midnight.
The Latin shortcut
Ante (before) + Meridiem (midday) = AM = morning. Post (after) + Meridiem = PM = afternoon/evening.
AM/PM in Digital Devices
Most smartphones and operating systems store time using the 24-hour clock internally. The AM/PM display is a formatting choice.
- iPhone/iPad (iOS): Settings → General → Date & Time → toggle 24-Hour Time.
- Android: Settings → System → Date & Time → Use 24-hour format.
- Windows: Settings → Time & Language → Region → Change date formats.
- macOS: System Settings → General → Language & Region → Time format.
Switching to 24-hour format eliminates AM/PM ambiguity entirely — every hour has a unique number from 0 to 23.