Solar calendar - Definition and Overview

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:

• Gregorian calendar
• Julian calendar
• Coptic calendar
• Iranian calendar
• Thai solar calendar

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:

• Hebrew calendar
• Chinese calendar
• Thai lunar calendar

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.