Measures in the primary curriculum

Exploring time - part 1

Measuring time

There are two quite different aspects of time that pupils have to learn to handle. First, there is the idea of a time interval. This refers to the length of time occupied by an activity, or the time that passes from one instant to another. Time intervals are measured in units such as seconds, minutes, hours, days, weeks, years, decades, centuries and millennia.

Then there is the idea of recorded time, the time at which an event occurs. To handle recorded time, we use the various conventions for reading the time of day, such as o’clock, a.m. and p.m., the 24-hour system, together with the different ways of recording the date, including reference to the day of the week, the day in the month and the year. So, for example, we might say that the meeting starts at 1530 on Monday, 7 October 2006, using the concept of ‘recorded time’, and that it is expected to last for 90 minutes, using the concept of ‘time interval’.

Time is one aspect of measurement that has not gone metric, so the relationships between the units (60 seconds in a minute, 60 minutes in an hour, 24 hours in a day, and so on) are particularly challenging. This makes it difficult, for example, to use a subtraction algorithm for finding the time intervals from one time to another. I strongly recommend that problems of this kind are done by an ad hoc process of adding-on.