Ask pupils to consider the divisions they have identified and define how they are similar and different. Draw a table on the board and ask pupils to classify the ways that we divide time today as either 'natural' divisions of time or 'constructed' divisions of time (or by some other system that they define collectively or individually).
Ask pupils to consider the need for these types of systems. Ask them to consider the ways that we use these systems.
Discuss the systems and mechanisms that we use today to keep track of time (e.g.: calendars, watches).
Discuss situations in which we rely on the accuracy of time. Discuss how the need for accuracy in measuring time has brought about the development of such systems and mechanisms.
Establish that there is a relationship between the need to measure time and the creation of 'constructed' divisions of time. Close the discussion by thinking about what the needs of the ancient Greeks might have been in terms of measuring timeBackground information: