Ekadashi (Sanskrit: एकादशी, ekādaśī, "Eleven"), also spelled as Ekadasi, is the eleventh lunar day (Tithi) of the shukla (bright) or krishna (dark) paksha (fortnight) of every lunar month in the Hindu calendar (Panchang). In Hinduism and Jainism it is considered a spiritually beneficial day. Scriptures recommend observing an (ideally waterless) fast from sunrise on the day of Ekadashi to sunrise on the day following Ekadashi.
Two Ekadashis occur in one month according to positions of the moon. The progression of the moon from full moon to new moon is divided into fifteen equal arcs. Each arc measures one lunar day, called "tithi": The time it takes the moon to traverse that distance is the length of that lunar day. Ekadashi refers to the 11 tithi, or lunar day. The eleventh tithi therefore corresponds to a precise phase of the waxing and waning moon: In the bright half of the lunar month, the moon will appear roughly 3/4 full on Ekadashi, and in the dark half of the lunar month, the moon will be about 3/4 dark on Ekadashi.
Bhagavata Purana (sk. IX, adhy. 4) notes the observation of Ekadashi by Ambarisha, a devotee of Vishnu.
List of Ekadashis 
The table below describes the Ekadashis and when they fall in the year.
|Vedic (Lunar) and Vaishnava Month
||Krishna paksha Ekadashi name
||Shukla paksha Ekadashi name
|Chaitra (चैत्र), Vishnu (March–April)
|Vaisakha (वैशाख), Madhusudana (April–May)
|Jyeshta (ज्येष्ठ), Trivikrama (May–June)
|Ashaad (आषाढ), Vaamana (June–July)
|Shraavana (श्रावण), Sridhar (July–August)
||Shravana Putrada Ekadashi
|Bhadrapada (भाद्रपद), Hrisikesha (August–September)
|Ashvin (अश्विन्), Padmanabha (September–October)
|Adika month (once in 2–3 years)
||Padmini Visuddha EkAdasii
|Kartik (कार्तिक), Damodara (October–November)
|Margashirsha (Agrahayana) (मार्गशीर्ष), Keshava (November–December)
|Pausha (पौष), Naaraayana (December–January)
||Pausha Putrada Ekadashi
|Maagha (माघ), Maadhava (January–February)
||Sat TilA Ekadashi
|Phalguna (फाल्गुन), Govinda (February–March)
Ekadashi calculation 
Ekadashi is different for Sri Vaishnavites and Smarthas. Whether Ekadashi is today, yesterday or tomorrow is determined by a formula. According to KalaPrakashika, a Jyotish text discussing Muhurta, auspicious times for beginning an activity, the Ekadashi fast is performed on a day which is not touched by or ruined by any influence of the tenth tithi or lunar day. The cut off time is 96 minutes before sunrise. If the tenth day is over at 96 minutes before sunrise, then that day is celebrated as Ekadashi. If the tenth day is not yet over at 96 minutes before sunrise, but begins sometime during that day, then the Ekadashi fast is performed on the following day. (Rules need to be included here by a Panchang Karta from Dharma Sindhu and Nirnaya Sindhu.)
See also 
Iyer, N.P. Subramania, Kalaprakasika: The standard book on the election (mahoortha) system: with original text in Devanagari and English translation, New Delhi: Asian Educational Services, 1982.
Gangadharan, N., Agni Purana, New Delhi: Motilala Banarsidass, 1985, Chapter 178.
External links