There are some other nations who continue to use their traditional calendars.
The Russian Orthodox church uses the Julian calendar – their New Year was on 14 January. The Hebrew calendar is a lunisolar calendar, with Rosh Hashanah (New Year) in September. The Jews believe that it will be 5782 years since the creation of the world.
The Chehalis are an indigenous people from British Columbia, Canada. They begin their count of lunar months from the arrival of spawning chinook salmon and count 10 months, leaving an uncounted period until the next chinook salmon run.
In Ethiopia they do not use the Gregorian calendar at all, they use a solar calendar all the time. This means there is gap of seven to eight years between Ethiopia and all other countries. Ethiopia begins their new year in September.
So, if you feel like it, you can celebrate Ethiopian New Year in September. It is not so very different – eating, drinking, parties – but each household also kills a sheep and a chicken.