March 25th, "Lady Day", used to be the start of the New Year

[Recursion]

This causes some headaches to historians, because what we think of as "January 2nd, 1590" they called "January 2nd, 1589" at the time.

Anyways, starting on March 25th you had three weeks to mark out the fields you were going to plow (the ground should be thawed by then), at which point you took your assessment to the local authorities and made your tax payment on it (generally a pledge in kind for the upcoming harvest). That's why, even in 2014, we still pay our taxes on April 15th.