## 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, such as one hour, 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 or 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 only to the hour and half hour.

The units for measuring time and relationships among them are as follows:

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

There are two systems for reporting 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; that is, calculating the interval of time that 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 also given to the hour. 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.

Calendar
Children learn that a calendar shows days, weeks, and months. At this grade level, children should be able to name the months of the year in order, as well as the days of the week.

Teaching Model 13.4: Half-Hour