English meaning of the festival
Skanda is another name for Kartikeya or Murugan. Sashti means six (referring to the 6th thithi on which this celebration is held).
How the date is decided annually
Skanda Sashti is held on the 6th date in the bright phase of the month of Kartik or Karthigai.
Significance of the festival to Hinduism
Skanda Sashti is a festival that honours the Lord Kartikeya. The festival signifies the victory of light over darkness. Skanda or Kartikeya has many attributes. He is most often depicted as six-faced. To Hindus, he is the supreme warrior and the commander-in-chief of the grand army of devas.
How to observe/practice
Devotees generally undertake a six-day fast leading up to Skanda Sashti. On Skanda Sashti, Skanda is worshipped with oblations of milk and other offerings.