With Easter falling on 31 March this year, a decision has been made to celebrate Sienese New Year on 8 April instead of the actual date, 25 March (Feast Day of the Annunciation). A change like this has indeed happened before, most recently in 2016.
From the 25 March post:
If you add 9 months to today, what do you get? That’s right, Christmas Day! So March 25th is the Feast Day of the Annunciation, which, until 1749, was the Sienese New Year. This was also the tradition in Florence, Pisa, and Lucca, and in other places beyond Tuscany too, but these towns preserved the tradition the longest (making dating documents sometimes confusing!). Ma perché? The Annunciation is when the Angel Gabriel comes down to the Virgin Mary and says, “Hail Mary, full of grace, God is with you.” This is the Incarnation, the Word made flesh, and the start of the Salvation cycle, which culminates in the Resurrection, Easter Sunday. In Christianity, therefore, it marks a new season of hope, as all mankind now has the chance to be redeemed.
If you’re anywhere in Tuscany, look out for people in historic dress processing towards the cathedral. In Siena, you’ll hear the drums and see the flags of the 17 Contrade as they go to the church of the Santissima Annunziata (Most Holy Annunciate) in the Hospital of Santa Maria della Scala, directly across from the Cathedral.