Understanding the calendar
Most confusion about Hindu dates comes down to three facts: a tithi is not a day, a lunar month is named differently in different regions, and each festival is governed by a different part of the day. Once those are clear, almost every "my calendar says something else" question answers itself.
Start here
- Tithi A lunar day — the time the Moon takes to gain 12° on the Sun.
- Nakshatra One of 27 star-segments the Moon passes through.
- Paksha The bright or dark fortnight.
- Vara The weekday.
- Vrat A vow — usually including a fast, but not only a fast.
Why dates move
- Vyapti Which part of the day a tithi must cover for the observance to fall there.
- Amanta A lunar month ending at the new moon.
- Purnimanta A lunar month ending at the full moon.
- Adhika Masa The extra lunar month, roughly every 32.5 months.
- Kshaya Tithi A tithi that never touches a sunrise, and is skipped.
The governing periods
- Nishita Kala The middle watch of the night.
- Pradosha Kala Roughly 90 minutes around sunset.
- Aparahna The afternoon — the fourth of five parts of the day.
- Madhyahna Midday — the third of five parts of the day.
- Arunodaya About 96 minutes before sunrise.
- Punya Kala A meritorious window around an astronomical event.
Daily timings
- Rahu Kalam A daily period traditionally avoided for beginnings.
- Yamagandam Another eighth of the day traditionally avoided.
- Gulika Kalam The period of Gulika (Mandi), a shadow point of Saturn.
- Abhijit Muhurta A short auspicious window around local noon.
- Dur Muhurtam An inauspicious muhurta, once or twice a day.
- Choghadiya Eight day and eight night periods, each with a quality.
- Hora The planetary hour.
The rest of the panchanga
- Yoga One of 27 combinations of the Sun's and Moon's positions.
- Karana Half a tithi; eleven names, four of them fixed.
- Bhadra (Vishti) A karana avoided for auspicious beginnings.
- Pada A quarter of a nakshatra.
- Sankranti The Sun's entry into a sidereal sign.
- Ghati A traditional time unit of 24 minutes.