The tradition of using a baby to personify the rebirth of a new year actually came from the Greeks, around 600 BC. Many cities would watch for the first baby of the new year, local merchants would shower it with gifts and the people would parade it through the streets. This practice was disapproved of by many mothers of the time, and later by early Christians, who believed it to be a continuation of pagan practices. Today there are no baby parades, but the symbolism continues with Baby New Year, often depicted in a diaper and top hat with a sash signifying the new year.
