Shattila Ekadashi is known by the sesame seed. Shat means six and tila means sesame, and the tradition names six ways of using sesame on the day: in the bath, in a paste put on the body, in the offering to the fire, in food, in water and in giving. It falls in the middle of winter, when sesame sweets are a part of the season anyway.
Shattila Ekadashi falls in the Krishna paksha, the waning fortnight, of Pausha in the amanta calendar (months that end at the new Moon). In the purnimanta calendar of north India, where the month ends at the full Moon, the same fortnight belongs to Magha.
The katha
For Shattila Ekadashi, as for the other named Ekadashis, the tradition points to the Padma Purana and the Bhavishyottara Purana, in which a teacher answers a king or a sage in turn, and printed versions differ in small details. The katha is a story about the difference between devotion and generosity.
A Brahmin woman had been devoted to Vishnu all her life, keeping vrats and praying with great sincerity. Yet she had never given food to anyone in need, thinking that her fasting was enough. Vishnu, wishing to teach her something kind, came to her door one day in the form of a beggar and asked for alms. She, annoyed at being disturbed, picked up a clod of earth and dropped it into his bowl.
When she died, her devotion took her to heaven, where she was given a small house, but it held no food whatsoever. She asked the gods why a woman of such faith should be left with an empty kitchen, and they reminded her of the clod of earth. They told her that the way to put it right was to hear from the women of heaven the method of Shattila Ekadashi, which they would tell if she opened the door of her house and listened.
She did so and kept the vrat with the six uses of sesame. The tradition says that her house was then filled with food and that she lived content. The meaning drawn from the tale is gentle: worship and generosity belong together, and a gift of food, even a small one, completes a vrat.
How the fast is kept
The six uses are the signature of the day. A common household version is to bathe with water in which a few sesame seeds have been put, apply a paste of sesame, offer sesame in a small fire or to the lamp, eat a sesame sweet such as a laddu, drink water in which sesame is steeped, and give sesame or food to someone in need.
Many people also feed the poor or give warm clothing on this day, since the story is about giving. Sesame is warming in the Ayurvedic view, which is one reason it suits the cold season.
Which day counts as Shattila Ekadashi depends on the school. Smarta practice, which the table follows, keeps the day when the tithi is running at sunrise; Vaishnava practice often rejects an Ekadashi that is mixed with Dashami before dawn and moves Shattila Ekadashi on by a day. The parana comes after sunrise on the next day, within Dwadashi and clear of Hari Vasara, and the Timing column shows the window for each city. On Shattila Ekadashi, how much you eat matters less than how you spend the day. If you need food or water for your health, take it without guilt, and check with your doctor before changing medicine or diet for any vrat.
Where it sits in the year
In the round of the year, Pausha Putrada Ekadashi comes before Shattila Ekadashi and Jaya Ekadashi after it. The Ekadashi page lists all the named Ekadashis. For Shattila Ekadashi the practical steps are in the Ekadashi vrat vidhi, and the meaning of the tithi is on the Ekadashi tithi page.