Sashti tithi is dedicated to Lord Skanda and the day is called as Skanda Sashti, it also called as Kanda Sashti. Skanda Sasti is one of the main festivals for Tamil Hindus.
Lord Subramanya is known as Skanda, Murugan, Kartikeyan. He is the son of God Shiva & goddess Parvathi. Skanda is considered as brother of Lord Ganesha. His vehicle is Peacock.
As per Hindu calendar, in every month during shukla paksha, sashti tithi (the sixth day in the bright half of the month) is considered as Skanda Sashti.
Skanda Sashti Vrat
When Sashti tithi(Sixth Lunar Day) is combined with Panchami tithi (Fifth Lunar Day) is preferred for Skanda Sashti Vrat. This has been mentioned in Dharmasindhu & Nirnayasindhu (Sacred writings of Hindu Religion).
Vrat is observed by devotees with fasting and performing puja to Lord Subrahmanya in temples or at home. Devotees takes only fruits, milk or any naivedyam offered to god as a food for the day.
In the lunar month of Karthika on Shukla Paksha Sashti is most significant for devotees. Devotees observe six day fast. Skanda Sashti in Kartika month is called as Soora Samhara and next day is called as Tiru Kalyanam.
Next Sashti after Skanda Sashti, i.e, in the lunar month of Marghashira is known as Subrahmanya Sashti.
Skanda Sashti Kavacham
People chants Skanda Sasti Kavacham on this day, it is composed by Sri Deva Raya Swamigal in 16th century to obtain the grace of Lord Murugan.