The Ancient Macedonian calendar is a lunisolar calendar that was in use in ancient Macedon in the 1st millennium BC. It consisted of 12 synodic lunar months (i.e. 354 days per year), which needed intercalary months to stay in step with the seasons. By the time the calendar was being used across the Hellenistic world, seven total embolimoi (intercalary months) were being added in each 19-year Metonic cycle. The names of the ancient Macedonian Calendar remained in use in Syria even into the Christian era. The Macedonian calendar was in essence the Babylonian calendar with the substitution of Macedonian names for the Babylonian ones. An example of 6th century AD inscriptions from Decapolis, Jordan, bearing the Solar Macedonian calendar, starts from the month Audynaeus. The solar type was merged later with the Julian calendar. In Roman Macedonia, both calendars were used. The Roman one is attested in inscriptions with the name Kalandôn gen. καλανδῶν calendae and the Macedonian Hellenikei dat. Ἑλληνικῇ Hellenic. Finally an inscription from Kassandreia of about ca. 306-298 BC bearing a month Ἀθηναιῶν Athenaion suggests that some cities may have used their own months even after the 4th century BC Macedonian expansion.
Year numbering
Under the Seleucid Empire, the Macedonians adopted the Seleucid era. The year beginning on the 1st of Dios during what we call October 312 BCE was declared to be the year one of the Seleucid era.