The Byzantine Empire used a year starting on 1 Sep, but they didn't count years since the birth of Christ, instead they counted years since the creation of the world which they dated to 1 September 5509 B.C.E. Since about 1600 most countries have used 1 January as the first day of the year.
Furthermore, who started the calendar year?
In 1582, when Pope Gregory XIII introduced his Gregorian calendar, Europe adhered to the Julian calendar, first implemented by Julius Caesar in 46 B.C. Since the Roman emperor's system miscalculated the length of the solar year by 11 minutes, the calendar had since fallen out of sync with the seasons.
Who discovered the first calendar?
British archaeology experts have discovered what they believe to be the world's oldest 'calendar', created by hunter-gatherer societies and dating back to around 8,000 BC. The Mesolithic monument was originally excavated in Aberdeenshire, Scotland, by the National Trust for Scotland in 2004.