The 24-Hour Clock Explained
The 24-hour clock counts hours from 00 to 23, with no am or pm. It is standard on UK train timetables and in the armed forces.
Converting
From 01:00 to 12:59 the 12-hour and 24-hour clocks match, except that 12:00 is noon. After noon, subtract 12 to get the pm hour: 15:00 is 3 pm, 18:30 is 6:30 pm. Midnight is 00:00, and 00:30 is 12:30 am.
Where you will see it
UK railways, airlines, hospitals and the armed forces use 24-hour times. In everyday conversation most people in the UK still say 12-hour times, and write them with am or pm.
Frequently asked questions
Is 24:00 the same as 00:00?
Both mean midnight. 24:00 usually marks the end of a day, and 00:00 marks the start of the next one.
Clock change guides
- What Is Daylight Saving Time (DST)? A Plain-English GuideWhat daylight saving time is, how it works in the UK, Europe and the US, why it exists, its history, who uses it and the argument over scrapping it.
- Why Do the Clocks Go Back in October? The Real ReasonThe clocks go back in autumn to return the UK to GMT, so winter mornings are lighter. The history, the rule, what time it happens and what changes for you.
- When Do the Clocks Go Forward Again After Going Back?When the UK clocks go forward again after the autumn change, how long the UK stays on GMT, when evenings get lighter and how to remember to reset your clocks.