Also, of the day and the month, and their relations to the rotation period of the Earth and the orbital period of the Moon. The differences between the solar year, the Julian calendar and the Gregorian calendar. Some facts about the calendar of the Maya culture, which thrived in Mesoamerica before Columbus. Tidbits about the holidays of the Russian church and of Islam.
Religions use calendars to set holidays.
People use them to mark birthdays and anniversaries City dwellers use calendars to keep schedules and appointments. The questions below may be used to guide the lesson and also in the review afterwards. A day is defined as the time between two corresponding positions of the Sun, e.g. from one noon to the next. Actually the time from noon to noon varies slightly, because of the uneven motion of Earth in its orbit. What clocks measure is the average day.