0000 vs 2400 Military Time: How to Write Midnight Correctly

Both 0000 and 2400 can refer to midnight, but they attach midnight to different calendar days. 0000 is the start of a date. 2400 is an end-of-day notation used in some schedules to close the preceding date.

The Same Instant, Two Labels

Consider midnight between August 14 and August 15:

• 2026-08-15 0000 means the beginning of August 15
• 2026-08-14 2400 can mean the end of August 14

Those labels identify the same boundary instant. The difference is which date the writer wants to emphasize.

When to Use 0000

Use 0000 when recording the beginning of a new day, entering a timestamp into software, or working with a system that accepts hours only from 00 through 23. It is the most interoperable choice.

In common military-style speech, 0000 may be read as “zero hundred hours” or “zero zero zero zero.” Style varies, so critical communication should include the date and time zone.

When 2400 Is Useful

An end time of 2400 can make a one-day schedule easier to read. A service shown as 0800–2400 clearly remains open through the final minute of that date. Writing 0800–0000 can look as though the end belongs to the same morning unless the next date is shown.

Not every database, programming language, or form accepts 2400. Many validators reject hour 24 because ordinary clock fields range from 00 to 23. Convert 2400 to 0000 on the following date before storing it in such a system.

Midnight and 12-Hour Time

In common usage, midnight is 12:00 AM, but that label is frequently misunderstood. For transportation, medicine, emergency operations, and international schedules, a date plus 0000 is clearer.

Common Errors

• Treating 2400 as noon; noon is 1200
• Writing 2401; after 2400 the clock continues as 0001 on the next date
• Changing 2400 to 0000 without advancing the date
• Recording midnight without a date
• Assuming every software system accepts hour 24

A Safe Rule

For data and general communication, write 0000 with the new date. Use 2400 only when a documented schedule permits it and the intent is to mark the end of the preceding date.