Attic Calendar

Attic Calendar allows you to track the calendar used in ancient Athens, including toggleable date markers for solstices and equinoxes, moon phases (as seen from Athens, Greece), and ancient Greek festivals and related events as recorded by Hellenion.
The calendar is calculated using the following rules:
1. The earliest supported Olympiad and year (Ol. 1.1) is defined as starting in the summer of 776 BCE.
2. For calculation purposes, days start at sunset as they did in ancient Greece, though for display purposes the days can start at midnight via the app's settings.
3. The start of a new month begins when a new moon is more than 20 hours before sunset. In other words, if the new moon was more than 20 hours before sunset, the sunset would start a new month, but if the new moon was less than 20 hours, the moon would be considered to not yet be visible to the naked eye and therefore the month would start the following day.
4. The beginning of a new year started at the beginning of a new month after the summer solstice.
5. In years with 13 months, the extra month has been added after Poseideon as Poseideon II, as was frequently done.
Note that historical dates are calculated using the above rules rather than referencing the specific dates used in the past. The Attic calendar was not always consistently modified in ancient Athens. For example, the intercalated 13th month could be inserted at different times in the year and with a different name. These variations are not captured in this app.
Though Hellenion festivals are supported by the app, the app is neither associated with nor produced by Hellenion.