Archives: World Calendars

Vikram Samvat is an era with multiple calendrical implementations rather than one uniform rule set across South Asia.

There is no single Hindu calendar. Regional variants can differ in month boundaries, year numbering, whether months begin near new or full moon, and other rules.

There is no single universal modern Zoroastrian calendar practice; communities may use different calendrical reckonings, which should be identified explicitly when converting dates.

The Jalali reform is famously associated with a group of astronomers including Omar Khayyam and is an important milestone in Persian solar calendrical history.

The Solar Hijri year is anchored to the spring equinox and shares its era origin with the Hijri tradition while using a solar, not lunar, year.

Umm al-Qura is distinct from a generic tabular Islamic calendar and from local observational determinations used elsewhere.

The tabular form provides deterministic dates without requiring local crescent observation, so it can differ from observed religious calendars.

Because it is purely lunar, the Hijri year moves through the seasons. Observational practice and calculated systems can produce differences of a day in month starts.

The Byzantine system is best understood as an era and year-numbering framework layered onto the Julian calendar rather than a wholly different month structure.

The traditional Armenian calendar belongs to the family of fixed 365-day systems used in the region and is important in medieval Armenian chronology.