Discuss the school timetable as an example of a calendar. Consider certain events e.g. sports day, and why it might change from year to year.
Look at the year calendar. How many festivals or special days can the pupils find? Divide them up into religious days and other days e.g. Easter, Queen's birthday. Compare these with previous year.
Look at alternative calendars, e.g. Christian, Muslim, Hindu, Chinese. Find out when new year starts in each. Get a year planner and put it on the classroom wall. Add festivals and events of the calendars using different colours. Explain that many cities in ancient Greece had different calendars. How could this cause problems?