Clocks, Calendars & Duration

On a clock face the short hand is the hour and the long hand is the minutes. For a quarter past five, the short hand is just past the five and the long hand points at the three — because for the long hand each number means five minutes, so one is five, two is ten and three is fifteen. That is clock A. The long hand pointing at three means fifteen minutes, not three minutes, and that is the mistake the test is fishing for. Always check the short hand as well, because a clock can have the minutes right and the hour wrong.

A digital clock writes the hour, then the minutes, so five fifteen is a quarter past five. The letters matter too: a.m. means before midday, so morning, and p.m. means after midday, so afternoon and evening. Five fifteen a.m. is before breakfast; five fifteen p.m. is after school. And notice that an analogue clock face cannot tell you whether it is a.m. or p.m. — only the words in the question can, so read them.

One and a quarter hours means one hour and fifteen minutes, because a quarter of an hour is fifteen minutes. So from ten o'clock in the morning, add the whole hour first to get eleven o'clock, then add the fifteen minutes to get a quarter past eleven. The answer is eleven fifteen a.m. Add the whole hours first and the minutes second — never try to do both at once, because that is where the mistakes come from.

To work out how long something took, hop up to the next o'clock first, then in whole hours. From half past nine to ten o'clock is thirty minutes, and from ten to eleven is one hour, so altogether it is one hour and thirty minutes. That is the same as ninety minutes. This is exactly the hopping you used for take-aways, just with times instead of numbers. Do read whether the question wants hours and minutes or just minutes, because one hour thirty and ninety minutes are the same length of time written two ways.

A calendar repeats every seven days, so the same weekday comes round seven, fourteen or twenty-one days later. If the third of July is a Friday, then the tenth, the seventeenth and the twenty-fourth are Fridays too. The twenty-seventh is three days after the twenty-fourth, so count on: Saturday, Sunday, Monday. The twenty-seventh of July is a Monday. Jump in sevens to get close, then count the last few days one at a time. That is all of it — clocks, am and pm, adding time on, working out how long, and calendars. Quiz and exercises now.