The New Year named after the Roman god Janus is celebrated in January.
January is the first month of the Gregorian calendar and begins immediately after December. Its name comes from Ianuarius, the Roman month associated with Janus, a god represented with two faces looking in opposite directions.
Janus was connected with doors, gates, beginnings, transitions, and endings. That symbolism made the name especially suitable for the first month of a year: one face could look back toward the past while the other looked forward toward what was beginning.
January was not always the first month in every Roman calendar. In the early Roman tradition, March held the leading position, but January and February were later placed at the beginning. The Gregorian calendar retained January 1 as New Year’s Day, while many cultures also observe lunar or religious New Year celebrations on different dates.