Have you seen all those English-speaking movies where characters kiss each other after the famous countdown? Well, it is a long-held tradition that dates back to ancient Rome as some historians say. The Romans knew how to party, and would throw a big celebration every year called the Festival of Saturnalia. Presumably, a lot of debauchery and kissing would happen, and this tradition filtered down to the rest of Europe. But there are other theories, check them out in the following link.