---
title: "12-hour and 24-hour time"
description: "Read, write, and convert time between analogue and digital 12-hour and 24-hour clocks"
canonical: https://lightmysky.com/learn/mathematics/12-hour-and-24-hour-time-mt_WfrE_4r-kY
source: https://lightmysky.com/learn/mathematics/12-hour-and-24-hour-time-mt_WfrE_4r-kY.md
retrieved: 2026-10-19
---

> **Agent view.** This is the Markdown twin of the page, for tools and assistants.
> When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md
> API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md
> Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt
> Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json
> Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`.

# 12-hour and 24-hour time

Read, write, and convert time between analogue and digital 12-hour and 24-hour clocks

Subject: Mathematics · Area: Measurement · Ages 8 to 9
Page: https://lightmysky.com/learn/mathematics/12-hour-and-24-hour-time-mt_WfrE_4r-kY

## Ready when they can

- Convert 3:45 pm to 15:45 in 24-hour time
- Read 19:30 and state the 12-hour equivalent as 7:30 pm
- Match a set of 12-hour and 24-hour times

## Lesson: 12-hour and 24-hour clocks

You have used clocks that count 1 to 12, with am for morning and pm for afternoon or evening. There is another way to write time called the 24-hour clock. It counts hours from 00 all the way to 23, so you never need am or pm.

*(drawing: This clock shows 15:45. In the 12-hour clock, that same time is 3:45 pm.)*

To change an afternoon or evening time into 24-hour time, add 12 to the hour. So 3:45 pm becomes 3 + 12 = 15, which is 15:45. Morning hours before noon stay almost the same. You just add a zero in front if the hour is a single digit, so 9:15 am becomes 09:15.

**Example.** A train leaves at 19:30. To find the 12-hour time, subtract 12 from the hour: 19 - 12 = 7. So the train leaves at 7:30 pm, in the evening.

**Tip.** Watch out for two special times. Noon is 12:00 pm, and midnight is 00:00 in the 24-hour clock. Neither one follows the usual add-12 or subtract-12 rule.

**Recap.** 24-hour time skips am and pm: add 12 to afternoon and evening hours, and keep morning hours almost the same.

## Practice

18 questions on this page, each with its working shown.

## Needs first

- [Telling time to five minutes with a.m. and p.m. (age 7+)](https://lightmysky.com/learn/mathematics/telling-time-to-five-minutes-with-a-m-and-p-m-age-7-mt_4m8BimI4G5)