Panchang & Muhurat5 min read · Updated 2026-06
The tithi or lunar day shapes Hindu fasts and festivals. Learn how tithis work and why Ekadashi is observed twice a month.
A tithi is a lunar day, defined by the Moon gaining 12° of angular distance from the Sun. There are thirty tithis in a lunar month, fifteen in the waxing fortnight (Shukla Paksha) and fifteen in the waning fortnight (Krishna Paksha), running from new Moon to full Moon and back.
Because the Moon's speed varies, a tithi can be a little shorter or longer than a solar day, which is why a tithi sometimes spans parts of two calendar days.
Each tithi has a name and a presiding influence, and many carry religious significance. Pratipada begins each fortnight; Purnima is the full Moon; Amavasya is the new Moon. The character of a tithi makes it suitable or unsuitable for particular activities in muhurat selection.
Festivals are fixed by tithi rather than by the solar date, which is why their position in the common calendar shifts each year.
Ekadashi, the eleventh tithi, falls twice each lunar month — once in the waxing and once in the waning fortnight. It is widely observed as a fasting day devoted to Vishnu, believed to purify the body and mind and to bring spiritual merit.
Each Ekadashi through the year has its own name and story, and the practice ranges from a full fast to abstaining only from grains. It is one of the most consistently kept observances in Hindu life.
A tithi is a lunar day, the time for the Moon to move 12° from the Sun, with thirty tithis in each lunar month.
The eleventh tithi occurs once in the waxing fortnight and once in the waning fortnight, giving two Ekadashis per lunar month.
Festivals are set by tithi in the lunar calendar, so their position in the solar (common) calendar shifts from year to year.
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