Merry Orthodox Christmas

Today is Christmas Day, if you're Eastern Orthodox, so I thought I should mention it here. The Eastern Orthodox (Greek Orthodox, Russian Orthodox, Ukrainian Orthodox, etc.) churches still observe Christmas on December 25^th by the Julian calendar, which is January 7^th by the Gregorian calendar. In the year 2101, Orthodox Christmas will move to January 8^th, because 2100 is a leap year in the Julian but not the Gregorian calendar. The date didn't change this century because both calendars agreed that 2000 was a leap year.

Of course, it's all just an approximation to the (northern hemisphere) winter solstice, which now falls on December 21 by the Gregorian calendar. Even if you believe that Jesus Christ was a specific historical individual, no reliable record exists of his exact date of birth, so the decision was made to have a party in the winter when people tend to feel gloomy. Drinking eggnog in the middle of summer would be just plain silly.