Sashti is another day of importance to Sri Murugan. It usually falls a few days after Amavasai (new moon). Devotees undertake fasts and offer prayers on this day every month for a period of time, usually a year or three years.

Since this day is of importance to Sri Murugan, the occurrence of Sashti during the month of Karthigai is considered of great importance and celebrated as Skanda Sashti. Special Poojas are held on this day at Sri Thendayuthapani Temple.