Janus, the ancient Roman god of beginnings and transitions, gave January its name in the Roman calendar. His name became the Latin word Ianuarius, which developed into English “January.”
Janus was commonly represented with two faces, one looking forward and one looking backward. That image made him especially appropriate for the turn of a year, when people reflect on the past and anticipate what comes next. His traditional associations included doorways, gates, passages, and changes of status.
January 1 became an important Roman civic date after calendar reforms and the scheduling of consuls’ terms made it the beginning of the political year. Julius Caesar’s calendar reform, introduced in 46 BCE and implemented in 45 BCE, helped standardize the date within the Julian calendar. The modern Gregorian calendar retains January as its first month.