In Denmark, smashing old plates against friends’ doors at New Year is traditionally meant to bring good luck.
The custom involves throwing unwanted crockery at the entrances of friends or neighbors. A large pile of broken dishes is traditionally interpreted as evidence that a household has many loyal friends who visited and left their old plates behind.
The practice is a folk tradition rather than an official national ceremony, and modern Danes do not all follow it. It is also commonly described alongside other Danish New Year customs, including jumping from a chair or sofa at midnight to symbolically leap into the new year.
Descriptions can vary by family and source, so the custom should not be treated as a universal Danish behavior. The important point is its symbolic association with friendship and luck, not simply the act of breaking crockery.