A tithi can begin at any hour, so one calendar day may hold two tithis. To pick the festival's day, the rule looks at one time of day: the time of the festival's own rite. Many festivals look at sunrise. The oil bath looks at the dawn before it, ancestor rites at the afternoon, lamps at the evening, and Shivaratri at midnight. For the date itself, the printed almanac of your tradition decides. A book's rule explains a date; it does not overrule the almanac.
☕ Each rite has its hour
A tithi is a lunar day. It does not start at midnight or at sunrise. It starts when the Moon has moved another 12° from the Sun, and that can be at any hour. So a festival's tithi often runs across two calendar days.
The rule then asks: on which day does the tithi hold at the time that matters? For many festivals that time is sunrise, the start of the Hindu day. For some, it is the time of the rite itself.
The Deepavali oil bath is taken before sunrise. Nirnaya Sindhu ranks the bath-times: the last watch of the night, then arunodaya, the dawn, then moonrise, each later one weightier (Nirnaya Sindhu of Kamalakara Bhatta, pp. 147–148). It gives arunodaya as four ghatikas. A ghatika is a nazhigai, 24 minutes.
Lamps are lit in the evening. Kalaprakasika says the lamps of the Krithikai festival are lit “about sunset”, that twilight is next, and “No illumination should be started later.” (Kalaprakasika (tr. N. P. Subramania Iyer, 1917), ch. XLIV, pp. 239–240).
The same day can therefore be right for one festival and wrong for another. That is why two almanacs can agree on every tithi and still print a festival on different days: they check different times.
At a glance
- Arunodaya, the dawn before sunrise: Deepavali Pandigai, Sri Vaishnava Ekadashi, Vaikunda Ekadashi Vratam.
- Sunrise: 26 festivals in Nava's list read the tithi or star at sunrise, some only as one test among others.
- The 12-nazhigai rule, read from sunrise: Yajur Veda Upakarma, Gayatri Japam, Sri Narasimha Jayanti.
- Aparahna, the afternoon: Sarva Amavasyai, Pournami, Sarva Mahalaya Amavasyai, Thai Amavasyai, Pagal Pathu Arambham, Sama Veda Upakarma, Sri Pancharatra Deepam, Ashtaka Tharpanam, Anvashtaka Tharpanam, Kedara Gauri Vratam, Soorasamharam, Hanumath Jayanthi, Vinayaga Chaturthi, Aadi Amavasya.
- Sunset: Karthigai Deepam, Sarvalaya Vaikhanasa Deepam, Pradosham.
- Pradosha, the evening after sunset: Karthigai Deepam, Pradosham.
- Nisitha, midnight: Maha Shivaratri, Masa Shivaratri.
- Arunodaya: the 96 minutes before sunrise, 4 nazhigai.
- Aparahna: the fourth of the five equal parts of daylight.
- Pradosha: Nava takes the 90 minutes after sunset, 3.75 nazhigai.
- Nisitha: the middle of the night, halfway from sunset to the next sunrise.
- What Nava does: every festival rule in Nava's list that reads a tithi or star reads it at one of these times, and the calendar reads the tithi or star at that time at your city's own sunrise and sunset.
Frequently asked questions
Why do so many festivals look at sunrise?
The Hindu day begins at sunrise, and the tithi at sunrise names the day in the almanac. A festival with no rite tied to another hour simply takes the day its tithi holds at sunrise.
Why does Deepavali look at the dawn and Karthigai Deepam at the evening?
Each looks at the time of its own rite. The Deepavali oil bath is before sunrise; the Karthigai lamps are lit at sunset. Nirnaya Sindhu places the bath before sunrise; Kalaprakasika places the lamps about sunset (Kalaprakasika (tr. N. P. Subramania Iyer, 1917), ch. XLIV, p. 239).
What is a nazhigai?
A nazhigai, or ghatika, is 24 minutes: sixty to a day and night. Two nazhigai make a muhurtham of 48 minutes. The festival rules measure in these units.
Does the time change from city to city?
Yes. Each time is counted from your own sunrise and sunset, so it moves with your city and the season. A tithi’s end is one moment everywhere, which is why a festival can fall on different days in different cities.
Deep dive: the windows on one day
The times on a day with sunrise at 06:00 and sunset at 18:00, and why the evening is split two ways.
🕰️ A sample day
Take a day with sunrise at 06:00 and sunset at 18:00. Nava's engine places the windows here:
- Arunodaya: from 04:24 to sunrise at 06:00.
- Aparahna: Nava reads it at 14:24, 7/10 of the way from sunrise to sunset.
- Sunset: 18:00. Pradosha: from sunset to 19:30.
- Nisitha: 00:00, the middle of the night.
On a real day every time moves with your sunrise and sunset.
🌇 Sunset, or the evening after it
Some rules ask what holds at the moment of sunset. Others ask what is present at any point in the evening window after it. Ahnika Grantham's Pradosham rule asks both: Trayodashi at sunset, and failing that, within six nazhigai after it (Ahnika Grantham, Vol. 1 (Sri Ahobila Mutt), p. 318).
Start with the tithi: what it is and why it runs across two days.