Silvester
Silvester (also spelled sylvester, szilveszter, or sylwester) is the day of the Feast of Pope Sylvester I, a saint who served as Pope of the Catholic Church from 314 to 335 and oversaw both the First Council of Nicaea and Roman Emperor Constantine I's conversion to Christianity. The feast day is held on the anniversary of Sylvester's death, 31 December, a date that, since the adoption of the Gregorian calendar, has coincided with New Year's Eve.
Eastern Orthodox Churches celebrate Sylvester's feast day on 2 January.