This created a dissociation of the calendar month from the lunation.
Amongst such calendar systems was the calendar system of the Persian Empire, which in turn gave rise to the Zoroastrian calendar as well as the Hebrew calendar.
A great number of Hellenic calendars developed in Classical Greece, and with the Hellenistic period also influenced calendars outside of the immediate sphere of Greek influence, giving rise to the various Hindu calendars as well as to the ancient Roman calendar.
A calendar can also mean a list of planned events, such as a court calendar or a partly or fully chronological list of documents, such as a calendar of wills.
Periods in a calendar (such as years and months) are usually, though not necessarily, synchronised with the cycle of the sun or the moon.
Calendars in antiquity were lunisolar, depending on the introduction of intercalary months to align the solar and the lunar years.
This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century Coligny calendar.
A full calendar system has a different calendar date for every day.
Thus the week cycle is by itself not a full calendar system; neither is a system to name the days within a year without a system for identifying the years.
A date is the designation of a single, specific day within such a system.
A calendar is also a physical record (often paper) of such a system.
The most common type of pre-modern calendar was the lunisolar calendar, a lunar calendar that occasionally adds one intercalary month to remain synchronised with the solar year over the long term.