Tonight Jews worldwide celebrate the Pesach Seder of the Jewish year 5766. Half meal, half religious ceremony, there will be prayers and songs, questions and games, unpallatable ritual herbs and bounteous feasting. Good times for all, on the whole.
Christians likewise celebrate Passover tonight, although they generally think of it as Maundy, or Holy, Thursday. In Christian tradition, the Last Supper is believed to have been a Pesach Seder meal, and most years the Thursday of Holy Week is the same day as the first day of Pesach. (Some years it's a week or so off, due to slight differences in how the two religions compute it.) A somber Mass is celebrated. Same idea, less food, but you can get your feet washed if you like.
When I got back to the physics building from the evening service, Campus Crusade's weekly Thursday Jesus Rock Sing-a-long was in full swing. This was quite the contrast. They weren't doing anything obviously different from their usual routine, though.