01What Vinayaka Chaturthi is
Vinayaka Chaturthi is the Chaturthi of the bright half of each lunar month, the monthly day for Ganesha as Vinayaka, the leader who goes before every undertaking. It comes once a month, twelve or thirteen times a year, about a fortnight after each Sankashti. The tradition marks the Vinayaka Chaturthi of Bhadrapada as Ganesh Chaturthi, the great festival of the birth of Ganesha, and keeps the others as smaller monthly observances in the same spirit. It is also called Vinayaki Chaturthi, and in parts of the north Varad Chaturthi, from varad, the giver of boons, one of his names.
02How the day and time are worked out
The worship of Ganesha on the bright half Chaturthi belongs to midday, the hour the tradition gives for his birth, so this page lists each Vinayaka Chaturthi on the day the Chaturthi tithi holds at midday. Midday here is the solar middle of the day for your city, halfway between sunrise and sunset, not noon by the clock. When Chaturthi covers midday on two days the first is taken, and when it covers none it is kept on the day it begins. Each entry shows when the tithi begins and ends, so the puja can be fitted inside it.
03How it is kept
The tradition keeps the monthly Vinayaka Chaturthi more lightly than Sankashti. Many fast until the midday puja or eat one meal, and worship Ganesha with durva grass in bunches of twenty-one, red flowers, sindoor and modak, reciting the Ganapati Atharvashirsha or the twelve names of Ganesha. Where Sankashti waits for the moon, Vinayaka Chaturthi asks the opposite: the tradition holds that the Moon should not be looked at on this night, after the story of the Moon laughing at Ganesha and being rebuked for it, a rule kept most strictly on Ganesh Chaturthi.
04The rest of the calendar