So far, walking in Germany has involved  puzzling over a lot of doors. We’ve seen these mysterious equations on a lot of the doors we’ve passed:

Equation in chalk, on a tiny blackboard at the top of a dark wood door

After a bit of Googling, we found out it’s part of a catholic tradition people have been following since the 1500s.

Kids dress up as one of the Magi (Casper, Melchior or Balthasar) and go door to door collecting for a good cause.

The letters are an abbreviation for the Latin ‘Christus maisonem benedictat’, which means ‘Christ blesses this house’. The ‘20’ and ‘17’ are this year so the last 2 numbers change each time. After they’ve done their rounds, the kids get to write the equation on the door.

Here are some more we’ve seen along the way.

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door

Equation in chalk, on a tiny blackboard at the top of a dark wood door