Teaching Models

Time and Calendar

One important part of learning to tell time is the association of daily activities with particular times of the day. It is also important to associate the meaning of a period of time with the time spent doing a particular activity, such as playing an instrument for one hour.

There are several mathematical concepts associated with measuring time. One is arranging events according to the times they take place. The terms before and after are the key terms in this context. Another concept is that of reading an analog clock or a digital clock or watch to tell what time it is. Times can be expressed as—o'clock, half-past—, fifteen minutes after—, twenty minutes before—, 10:25, and so on. At this grade level, children read and express time in five-minute intervals.

The units for measuring time are as follows.

1 minute = 60 seconds
1 hour = 60 minutes
1 day = 24 hours
1 year = 365 days

There are two systems for recording time. One way is to use hours from 1 to 12 and use a.m. (Latin, ante meridiem) for times before noon and p.m. (Latin, post meridiem) to indicate times after noon. The other way is to use hours from 1 to 24 accounting for the times in the 24-hour period. Thus, 9:00 p.m. in the 12-hour system would be shown as 21:00 in the 24-hour system.

Still another concept is that of calculating elapsed time, the interval of time that has passed between a beginning and ending of an event. At this grade level, elapsed time is found by counting on from the time given to the hour to another time. For example, finding the elapsed time between 2:00 p.m. and 4:00 p.m. can be done by using the clock and counting on from 2:00 by saying “3 o'clock, 4 o'clock.” Thus, the elapsed time from 2:00 p.m. to 4:00 p.m. is 2 hours.

At this grade level, children review the months of the year and days of the week when working with a calendar. They learn to associate each month with an ordinal number, such as September as the ninth month of the year. Children also begin to compare longer time periods, deciding whether, for example, 2 months or 75 days is the longer period of time. They also estimate the time period needed to complete an activity, such as whether it would take hours or weeks to grow a garden.

Teaching Model 16.3: Time to Five Minutes

Houghton Mifflin Math Grade 2