How to Write Midnight in 24-Hour Time
Updated June 15, 2026
The standard way to write midnight in 24-hour time is 00:00. In military contexts, it is written as 0000 (no colon). Some schedules use 24:00 to mark the end of a day. The right format depends on where you are writing it.
Direct answer
Write 00:00 for most purposes. Write 0000 for military or aviation contexts. Write 24:00 only when you need to clearly mark the end of a day. Avoid writing midnight as 0:00 (single zero) — always use two digits for the hour. 00:00 in 12-hour time is 12:00 AM.
The four ways to write midnight
| Format | Example | Used by | Note |
|---|---|---|---|
| 00:00 | 00:00 | International standard, civilian | The ISO 8601 standard. Always use two zeros for the hour, a colon, then two zeros for minutes. |
| 0000 | 0000 | Military, aviation, dispatch | Four digits, no colon. Spoken as "zero hundred hours." This is the NATO standard. |
| 24:00 | 24:00 | Schedules, deadlines, Japan | Non-standard but recognized. Means the end of a day, not the start of the next. |
| 12:00 AM | 12:00 AM | United States, general public | 12-hour notation. Ambiguous without the AM label. Avoid in technical contexts. |
Aviation: always 0000
In aviation, every time is written as a four-digit Zulu (UTC) value without a colon. Midnight is 0000Z. A flight plan filed for 0000Z means the aircraft intends to depart at midnight UTC. There is no 2400 in aviation — the day runs from 0000 to 2359, then resets.
Pilots say "zero zero zero zero Zulu" or simply "zero hundred Zulu." The Z suffix is pronounced "Zulu" and means the time is in UTC, not local.
Military: 0000, spoken as "zero hundred"
The US military and NATO forces write midnight as 0000 (always four digits). On duty rosters, after-action reports, and operations orders, you will see times like 0000, 0030, 0100. The colon is never used.
For spoken communication, 0000 is "zero hundred hours" or "zero hundred." 0030 is "zero thirty." In informal settings, soldiers may say "oh-dark-thirty" for times in the early morning, but this is slang, not official terminology.
Medicine and nursing: 00:00 or 0000
Hospitals and nursing stations use both formats — sometimes on the same shift. The key priority in medicine is to never abbreviate midnight in a way that could be misread.
What to avoid in medical writing
- Never write just "12:00" without AM or PM — it could mean noon
- Never write "0:00" with a single zero — it looks like a typo
- Never use "MN" or "Mid." as abbreviations for midnight — they are not universal
- Always double-check that the MAR (medication administration record) time matches the order
Most modern EMR (electronic medical record) systems use 24-hour time with the colon: 00:00, 00:15, 00:30. Nurses documenting on paper often use the four-digit military format: 0000, 0015, 0030.
Everyday writing: keep it simple
If you are writing an email, a calendar invite, or a note to a friend, the clearest option is often just the word "midnight" followed by the time zone: "The deadline is midnight EST."
If you must use a numeric format, pick 00:00. It is the international standard, it is unambiguous, and it works across all devices and software. Avoid 24:00 in everyday writing unless you specifically want to emphasize the end of a day, such as "The promotion ends at 24:00 on Friday."