January is named after Janus, the Roman god associated with beginnings, transitions, doorways, and passages. His symbolism made him a fitting figure for the month that opens the Roman and modern Gregorian year.
Janus was commonly represented with two faces: one looking forward and the other looking backward. This image is why New Year's reflections and plans are often connected with the god, although the ancient Romans did not celebrate January 1 in exactly the same way modern societies do.
The Roman calendar originally began in March, but January became the first month in the later Republican period. The Julian calendar reforms under Julius Caesar helped establish January 1 as the start of the civil year. The Gregorian calendar, introduced in 1582 and now widely used internationally, retained that arrangement. Janus is distinct from Saturn, whose festival Saturnalia took place in December.