Why January 1 Became the Start of the New Year

The choice of January 1 as New Year's Day has roots in ancient Roman traditions and the evolution of calendars over millennia.

The tradition of celebrating New Year's on January 1 originates from the Roman god Janus, symbolizing beginnings and transitions, after whom the month of January is named.
The Julian calendar, introduced by Julius Caesar in 46 BCE, officially established January 1 as the start of the civil year, replacing earlier calendars that began in March or tied the new year to equinoxes or solstices.
The Gregorian calendar, introduced by Pope Gregory XIII in 1582, corrected inaccuracies in the Julian calendar and reaffirmed January 1 as New Year's Day, a standard now used globally for civil purposes.
Ancient cultures celebrated the new year at different times, such as Mesopotamians in March, Egyptians in mid-July, and Chinese traditions tied to lunar cycles in late January or February.
The practice of New Year's resolutions traces back to Roman customs of making promises to Janus, reflecting on the past year, and setting intentions for the year ahead.