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A solar calendar is a calendar whose dates indicate the
season and so are synchronized to the declination of the sun. The mean calendar year approximates the tropical year.
The following are solar calendars:
Every one of these calendars has a year of 365 days, which is occasionally extended by adding an extra day to form a leap year.
The following are lunisolar calendars; they have dates that
also indicate the moon phase:
Calendars that are not solar calendars, include the Islamic
calendar which is a pure lunar calendar and calendars synchronized
to the synodic period of Venus or to the heliacal risings of stars.
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