Most of the world uses the Gregorian calendar for civil life, but billions of people also follow lunar, lunisolar and solar religious calendars. Here is how the major systems work.
Gregorian — the global standard
The Gregorian calendar is a solar calendar of 365 days (366 in a leap year), introduced in 1582. It is the international civil standard and the default on the live calendar.
Islamic (Hijri) — purely lunar
The Islamic Hijri calendar has 12 lunar months and about 354 days, so its dates fall ~11 days earlier each Gregorian year. It sets Ramadan and Eid. A related solar reckoning powers the Persian (Solar Hijri) calendar.
Chinese & Hindu — lunisolar
The Chinese calendar and the Hindu calendar are lunisolar: they follow the Moon but add a leap month to stay aligned with the seasons. They fix Chinese New Year, Diwali and many festivals. South India also keeps the Tamil calendar, and Bengal the Bangla calendar.
Hebrew, Buddhist & Ethiopian
The Hebrew calendar is lunisolar and sets the Jewish holidays. The Buddhist calendar counts years from the Buddha's passing. The Ethiopian calendar has 13 months and runs about 7–8 years behind the Gregorian year.
See today in every system
Each calendar above has a live page on caldays with today's date and upcoming festivals — start from the Gregorian calendar and switch systems from there, or check the Moon phase today that drives the lunar calendars.
FAQ
Why do Islamic dates shift every year? The Hijri calendar is lunar (~354 days), so it drifts ~11 days earlier against the solar Gregorian calendar each year.
What is a lunisolar calendar? One that follows the Moon's phases but inserts an extra month every few years to stay in step with the seasons — like the Chinese and Hebrew calendars.