Daylight Saving

Purpose To compare standard time (sun-time) and DST.

Materials

hammersundial

3-inch (7.5- cm) 16d nail or other long nail

2-by-4-by-6-inch (5-by-10-by-15-cm) wooden block.

watch

2 markers -1 black, 1red

adult helper

Procedure

1. Ask your adult helper to hammer the tip of the nail near one end of the wooden block. The nail should be firm and vertical as possible without being driven in too deeply. This is a sun clock.

2. On a sunny day during the week before DST starts, take the sun clock outdoors about 5 minutes before 9 o’clock am. (or any convenient hour). Note the direction of the block.
3. Set the sundial in a sunny area. The position of the sundial is very important and must be placed in the exact place in order to repeat the activity during DST.

4. Use the black marker to trace the shadow of the nail where it falls across the wooden block. Note the time on your watch and write it on the shadow line.

5. On a sunny during the first week of DST, set the sundial in the same position as in step 3 about 5 minutes before 10 o’clock am.

6. Using the red marker, repeat step 4.

7. Compare the shadow lines and the clock times for each.

Results

The shadow lines are close to each other or overlapping, but the clock times are different by 1 hour.

Why?

While the shadow lines are the same or nearly so, the clock time differs by one hour. Before DSL starts, sun time is 1 hour earlier than clock time. This means that when a shadow is marked at 9 am before DSL starts, the Sun is in approximately the same position in the sky at 10 am during DSL.