A new year begins at the first new moon after the vernal equinox. This year (2020), that date is March 25th. Interestingly, the Julian calendar always started the year on March 25th, which, to me, indicates the very important influence of the Bible and Hebraic understanding of time to this calendar, though that static date eventually led to some misalignments with the sun, moon, and stars, . Though there are a very few regions which still hold to the Julian calendar, by and large, the rest of the world had begun using the 1582 Gregorian decreed calendar and by 1752, it was adopted by decree by the British and her colonies, including America, though the Quakers held to the Julian for some time. Two major shifts were to change the head of the year from March 25th to January 1 and by 1752, eliminate 10 days; those selected were September 3-13.
For further study:
Calendar Confusion by Steve Moutria
The Calendar in 1752 looks very strange!