Karva Chauth is observed mainly by married women across the north and northwest. The fast is nirjala, taken from before dawn without food or water, and is broken only after the moon has risen and been viewed, traditionally through a sieve, followed by a first sip of water and a morsel offered by the husband. The day includes a gathering where an earthen pot, the karva, is passed around and the story of the fast is told.
It falls on the fourth tithi (Chaturthi) of the waning fortnight of Kartika in the Purnimanta calendar, four days after the full moon. Because moonrise on this night is comparatively late and shifts with longitude, the time the fast ends differs by an hour or more between cities.
The practice is regionally concentrated in Punjab, Haryana, Rajasthan, Delhi and western Uttar Pradesh; in Rajasthan and parts of the west the associated evening rite is Sargi and the pre-dawn meal has its own local forms.