Saturday 15th March in Roman tradition was the celebration of Anna Perenna. Offerings were made to the Spirit of the Year, so that the circle could be completed. 15th March is also the Ides of March in Roman tradition and a Festival to Jupiter. Shakespeare had a soothsayer warn Julius Caesar 'Beware the Ides of March' and indeed he was reputedly assassinated on 15th March 44 BC.
Saturday 15th March (sunset) until Sunday 16th March (sunset) is also the Jewish Ceremony of Purim. This is the Spring Carnival celebrating the averting of a Persian Massacre. It is traditional to have a feast and dress up in costumes and masks.