A custom in homes of many countries including Austria, Czechia, Slovakia, Germany, Hungary, Poland and Sweden, is to inscribe the letters CMB above the front door, placing a cross between each letter, framed by the date of the current year:          

20 +  C + M + B + 20 .

This is done each year on January 6, the Epiphany, commemorating the wise men led by a star to the new born Jesus. Legend has it their names were Caspar, Melchior and Balthazar. Many people interpret the three letters as the initials of those names. In reality these letters originate from the Latin phrase Christus Mansionem Benedicat (May Christ bless this home). This religious custom expresses the belief that the Lord remains close to his people throughout the year.