Susan Steward, age 9, for her question:

Where does the day begin?

The earth is a round ball, spinning around like a top. First one side, then another turns to face the radiant sun. When your side of the earth faces the sun' you are in daylight. But the earth keeps on turning. Your side turns to face away from the sun into the shadows of night. Meantime the people on the opposite side of the globe are having daylight. The earth keeps on turning and soon you come around to face the daylight and the opposite side of the globe has night.

The earth turns around once every 24 hours but there is no mark to show where each turn begins or ends. The earth does not give us a clue to mark the beginning of each day. But we must have this information to mark off the dates on the calendar. So, we make up a mark to show whets the day begins. Each calendar day begins at the International Date Line, down the Pacific Ocean. Today, and every other date begins at this line.