Telling Time and Elapsed Time

The idea in one sentence

The short hand tells you the hour, the long hand tells you the minutes, and the whole thing counts in sixties rather than tens.

Two hands, two scales

The same twelve numbers on the face mean different things depending on which hand is pointing at them. That’s the difficulty, and saying it out loud usually fixes it.

• The hour hand is short and slow. It points at, or just past, the current hour.
• The minute hand is long and fast. When it points at the 3, it means 15 minutes, not 3.

Each number is 5 minutes apart for the minute hand, because 12 numbers spread over 60 minutes is 5 minutes each. Counting round by fives is the whole skill: 5, 10, 15, 20, and so on.

The hour hand moves too, gradually. At half past two it sits between the 2 and the 3, not on the 2 — which is a useful check. If the minute hand says half past and the hour hand is sitting exactly on a number, the clock is drawn wrong.

The words

That last row is the trap. At 2:45 you say “quarter to three”, because you’re describing how long until three o’clock. Past the half hour, the phrasing switches from counting up from the hour to counting down to the next one.

24-hour time

The clock face repeats twice a day, so 3:00 is ambiguous without am or pm. Twenty-four-hour time removes the ambiguity: afternoon hours carry on past 12, so 3pm is 15:00.

To convert an afternoon time, add 12 to the hour. To convert back, subtract 12 from anything above 12. Timetables, alarms, and computers all use it precisely because it can’t be misread.

Elapsed time

How long from 10:45 to 13:20? Don’t subtract in columns — minutes aren’t tens, and borrowing across a base-60 boundary goes wrong.

Count on through the friendly landmarks instead:

• 10:45 to 11:00 is 15 minutes
• 11:00 to 13:00 is 2 hours
• 13:00 to 13:20 is 20 minutes

Total: 2 hours 35 minutes. Jump to the next whole hour, then count whole hours, then the remaining minutes. The same counting-on move that makes change from a £5 note.

Common mix-ups

• Reading the minute hand as the number it points at. Multiply by 5.
• Confusing the hands. Short is hours.
• Subtracting times in columns. 60 minutes make an hour, not 100.
• Saying “quarter past” after the half hour. Past the 30, count down to the next hour.

Check yourself

A film starts at 18:40 and lasts 1 hour 50 minutes. When does it finish?

18:40 plus 20 minutes reaches 19:00; 1 hour more is 20:00; 30 minutes more is 20:30 — that’s 8:30pm.