Why did britian used to use the Julian calender?

by LoanFrosty733

Apparently new years way on March 25th. Where does this date come from, why did England use it and why did UK change to gregorian calender?

WelfOnTheShelf

There was a similar question that I answered a few weeks ago, hopefully it will be helpful:

In England, from 1155 to 1752, the new year started on March 25. Why?