The term Hijri calendar has more than one meaning. There are three calendars that have the Hijrah as their epoch
In most Islamic countries
- The Islamic calendar, the lunar calendar based on actual lunar observation. It is does not take account of the seasons
- The Tabular Islamic calendar, a rule-based variation of the Islamic calendar. It has the same numbering of years and months, but the months are determined by arithmetical rules rather than by observation or astronomical calculations.
- The Solar Hijri calendar, whose year begins at the moment of the Spring equinox in the northern hemisphere.