Tithi: The Thirty Lunar Days, Their Nature and Their Uses

From one new moon to the next is a lunar month of thirty tithis. A tithi ends each time the Moon moves another 12° away from the Sun. The tithi named in the panjika is usually the one prevailing at sunrise, though for rituals the exact start and end moments are also checked.

Five groups

The same five groups repeat three times: Pratipada to Panchami, Shashthi to Dashami, and Ekadashi to Purnima or Amavasya.

The "Bhadra" tithi group and the Bhadra (Vishti) karana share a name but are different things: the karana is avoided, the tithi group is auspicious.

Strength by fortnight

In the bright fortnight the Moon grows; in the dark fortnight it wanes. For auspicious work the period from Shukla Dwitiya to Krishna Panchami is generally preferred, when the Moon is bright and strong. Late in the dark fortnight it is faint, and at Amavasya invisible.

Some special tithis

Ekadashi: twice a month, once in each fortnight; a day of fasting and worship of Vishnu. In Vaishnava practice Ekadashi must prevail at sunrise, and if the previous Dashami lingers past sunrise that Ekadashi is skipped for the next day. That is why two almanacs sometimes show different Ekadashi dates.

Amavasya: the Sun and Moon at the same point. A day for offerings to ancestors, Kali Puja and tantric practice; generally avoided for new beginnings. When it falls near Rahu or Ketu there is a solar eclipse.

Purnima: the Moon exactly opposite the Sun. Many festivals fall on it: Lakshmi Puja, Rasa, Dol and Buddha Purnima. Near Rahu or Ketu it brings a lunar eclipse.

Paksha randhra: Chaturthi, Shashthi, Ashtami, Navami, Dwadashi and Chaturdashi are the paksha randhra tithis; Ashtami and Chaturdashi above all are avoided for weddings and similar events.

Tithi and weekday together

Some tithis form special yogas on particular weekdays. Dwadashi on a Sunday or Ekadashi on a Monday is dagdha yoga, to be avoided. Nanda tithis on Friday, Bhadra on Wednesday, Jaya on Tuesday, Rikta on Saturday and Purna on Thursday make siddha yoga, held to bring success. Almanac makers weigh these when choosing muhurtas.

Where to see today's tithi

Suvolagna's today's panchang shows each day's tithi and when it ends, in Dhaka time; the month calendar marks Ekadashi, Purnima and Amavasya.