In Ready For Midnight, from the (free) subscription-based Fairfax Digital, Caesar is credited with moving the New Year from the Vernal Equinox to January 1 and the Babylonians are credited with the first New Year's resolutions:
"They have changed in focus, but New Year’s resolutions go back about 4000 years, when the ancient Babylonians resolved to return any farming equipment they borrowed during the year to their rightful owners in time for the start of the new year — new year then, of course, being the vernal equinox."