If we keep the same calendar that is used in "the Western Civilization", then consider the following:
September literally means "the 7th month" (Septem = 7 in Latin)
October = "the 8th month"
November = the 9th month
December = the 10th month (Decem = 10 in Latin)
Go back far enough (before Julius Caesar) and there were also Quintilis (the 5th month, now July) and Sextilis (the 6th month, now August).
Work backwards, and you get March 1 as the beginning of the year... as it was in Rome before the Church took control.
March (Mars = Martius) was named after the god of war; it was the earliest month when the armies could use the roads to go out and conquer more territory (winter = mud and lousy weather).
For a while, the two months of winter did not have official names, except in the religious calendar of celebrations where Janus was a two-faced god capable of looking to the past (the previous year and the upcoming new year) -- he was also the god of doors (being able to see comings AND goings).
February was the month of "febrility" (fevers). Because it became the last month of the year, it was the one to be left with only 28 days and to have the extra day added every 4 years.
Therefore, I vote for March 1 (= kalenda Martii)