Saint Sylvester's Day, also known as Silvester or the Feast of Saint Sylvester, is the day of the feast of Pope Sylvester I, a saint who served as Pope from 314 to 335. Medieval legend made him responsible for the conversion of emperor Constantine. Among the Western churches, the feast day is held on the anniversary of Saint Sylvester's death, 31 December, a date that, since the adoption of the Gregorian calendar, has coincided with New Year's Eve. For these Christian denominations, Saint Silvester's Day liturgically marks the seventh day of Christmastide. Eastern churches celebrate Sylvester's feast on a different day from the Western churches, i.e. on 2 January. Saint Sylvester's Day celebrations are marked by church attendance at a Watchnight Mass that is often held around midnight, as well as fireworks, partying, and feasting.