January -- Janus's month Middle English Januarie Latin Januarius "of Janus" Latin Janu(s) "Janus" + -arius "ary (pertaining to)" Latin Januarius mensis "month of Janus" Janus is the Roman god of gates and doorways, depicted with two faces looking in opposite directions. His festival month is January. Januarius had 29 days, until Julius when it became 31 days long.
Janus - God of change and time e.g future to past, one condition to another, from one vision to another, and young people's growth to adulthood. He represented time, because he could see into the past with one face and into the future with the other. Janus was worshipped at the beginnings of the harvest and planting times, as well as at marriages, deaths. He represented the middle ground between barbarism and civilization, rural and urban, youth and adulthood.
Janus - In ancient Roman religion and mythology, Janus (Latin: Ianus) is the god of beginnings and transitions, thence also of gates, doors, doorways, endings and time. He is usually a two-faced god since he looks to the future and the past. The Romans dedicated the month of January to Janus. Source: Wikipedia