13 February
Idus Februarias, a Roman holiday, falls on what is now the 13th of February in our modern Gregorian calendar.
The Ides were a religious festival that actually went on for 9 days, from the 13th through to the 21st February inclusive. The first day, the 13th, was called the "Idus Februarias"; the entire period was called the "parentalia."
This was a period to honour your ancestors with offerings at their tombs. Romans would leave flowers, a trickle of wine, bread crumbs, or a sprinkle of salt.
The entire month of February was dedicated to Mars and Juno.