Top Tips for Teaching Kids the 24 Hour Clock

How to Read and Convert the 24 Hour Clock QuicklyThe 24 hour clock (also called “military time” in some countries) runs from 00:00 to 23:59 and is used worldwide in transport timetables, medicine, computing, and many workplaces because it removes ambiguity between morning and evening times. This article gives clear rules, practical shortcuts, common pitfalls, and practice exercises so you can read and convert the 24 hour clock quickly and confidently.

Quick overview: format and basic rules

• The 24 hour clock uses four digits (HH:MM). Hours go from 00 to 23 and minutes from 00 to 59.
• 00:00 represents midnight at the start of the day; 12:00 is noon; 23:59 is one minute before midnight.
• Leading zeros are used for single-digit hours (for example, 06:30).

Converting 24-hour to 12-hour (readable fast)

1. If the hour is 00, read as 12 AM (midnight hour).
   • Example: 00:15 → 12:15 AM.
2. If the hour is 01–11, read the same hour as AM.
   • Example: 09:45 → 9:45 AM.
3. If the hour is 12, read as 12 PM (noon hour).
   • Example: 12:00 → 12:00 PM.
4. If the hour is 13–23, subtract 12 and read as PM.
   • Example: 18:20 → 6:20 PM (18 − 12 = 6).

Memory shortcut: for PM times, drop the leading “1” for 13–19 and subtract 12 for 20–23; for example, 17 → 5 PM, 20 → 8 PM.

Converting 12-hour to 24-hour quickly

1. For AM times:
   • If it’s 12 AM, convert to 00:MM (midnight).
     • 12:30 AM → 00:30.
   • For 1 AM–11 AM, use the same hour with leading zero if needed.
     • 7:05 AM → 07:05.
2. For PM times:
   • If it’s 12 PM, keep as 12:MM (noon).
     • 12:45 PM → 12:45.
   • For 1 PM–11 PM, add 12 to the hour.
     • 3:10 PM → 15:10 (3 + 12 = 15).

Fast trick: for PM (except 12 PM), mentally add 12; for 12 AM, swap 12 → 00.

Reading aloud and writing times

• Formal/readable style: write “14:30” or say “fourteen thirty.” In casual 12-hour speech you’d say “two thirty PM.”
• When reading minutes less than 10, include the zero: 09:05 → “zero nine oh five” in precise contexts (e.g., aviation) or “nine oh five” in casual speech.

Common real-world examples and contexts

• Travel schedules: trains and flights almost always use 24-hour time in timetables (e.g., 06:00 departure, 21:15 arrival).
• Medicine/hospitals: 24-hour time reduces medication/treatment errors.
• Computing/logs: timestamps use 24-hour time to avoid AM/PM ambiguity (e.g., 2025-09-02T18:30:00).
• Military/emergency services: spoken as “zero six hundred” (06:00) or “one eight hundred” (18:00) for clarity.

Fast mental tricks and patterns

• Hours 13–19: drop the leading 1 to get the PM hour (13→1, 14→2, … 19→7).
• Hours 20–23: subtract 12 as usual (20→8, 21→9, 22→10, 23→11).
• If you frequently convert, practice by mapping common times: 07:00, 12:00, 15:30, 18:45, 23:59.
• Use visual grouping: imagine the clock split in half — 00–11 (AM), 12–23 (PM).

Common mistakes to avoid

• Confusing 00:00 and 24:00 — use 00:00 for the start of the day; some systems allow 24:00 to denote the end of a day but it’s less common.
• Forgetting that 12:00 is noon (12 PM), not midnight.
• Dropping leading zeros in formal contexts where four-digit format is expected (e.g., writing 7:05 instead of 07:05).

Practice exercises (with answers)

1. Convert to 12-hour: 00:45 → 12:45 AM.
2. Convert to 12-hour: 13:00 → 1:00 PM.
3. Convert to 24-hour: 11:30 PM → 23:30.
4. Convert to 24-hour: 12:00 AM → 00:00.
5. Convert to 12-hour: 12:15 → 12:15 PM.

Quick-reference cheat sheet

• 00:00 = 12:00 AM (midnight)
• 01:00–11:59 = 1:00 AM – 11:59 AM
• 12:00 = 12:00 PM (noon)
• 13:00–23:59 = 1:00 PM – 11:59 PM

If you want, I can convert a list of times for you, create printable flashcards for practicing conversions, or give a short quiz to test speed.