Attic Calendar - Sidereal Calendar

Sidereal Calendar

A third calendar regulating Athenian lives was solar or seasonal. As such, it was fundamental for seasonal activities like farming and sailing. Within the broad divisions of the seasons, it relied on star risings and settings to mark more precise points in time. Star risings are the days when particular stars or constellations that have been below the horizon during hours of darkness first appear after sunset. Different star risings were keyed to various farm tasks, such as when to harvest: Hesiod in the Works and Days urges the farmer to harvest when the Pleiades rises (an event which elsewhere is set to mark the end of spring). Such a system was part of general Greek tradition, but fitted to local geography and conditions.

The seasons were not viewed by Greeks as dividing the year into four even blocks, but rather spring and autumn were shorter tail sections of the overarching seasons, Summer and Winter. These divisions could be formalised by using star risings or settings in relation to the equinoxes: so for instance, winter is defined in one medical text as the period between the setting of the Pleiades and the spring.

The older tradition as seen in Hesiod's Works and Days was extended by astronomical research to the creation of star calendars known as parapegmas. These were stone or wooden tablets listing a sequence of astronomical events, each with a peg hole beside it. Lines of bare peg holes were used to count the 'empty days' between what were taken as the significant celestial events. Often set up in town squares (agora), these tablets put the progression of the year on public display.

This system would have been fundamental to an individual's sense of the advancing year, but it barely intersected with the festival or state calendars. These were more civic in character and required managing to maintain their coherence with the year of the seasons. The seasonal and sidereal calendar, on the other hand, was immune to interference. So, Thucydides can date by the rising of the star Arcturus without having to wade into the confusion of disconnected city-state calendars.