For Catholics: NBC is broadcasting Midnight Mass from the Vatican at 11:30 tonight...

First chronicled by the Galician pilgrim Egaria in the year AD 381, priests would say mass in the open outside the Church of the Nativity in Bethlehem and then lead a torchlit procession to Jerusalem where they would arrive outside the Church of the Resurrection at dawn on Christmas Day. By the year 430 the practice had arrived in the western empire, with Pope Sixtus III being the first Roman pontiff to celebrate Midnight Mass in the Basilica of St. Mary Major.

While traditionally known as "Midnight Mass," the official name of the service is actually Ad Missam in nocte (Mass during the Night) and can take place at anytime during the evening. For instance: the Vatican celebrates the service at 10 PM local. As I type this they are wrapping up the service with a rendition of Silent Night.