Another religious celebration attached to one of these calendar events was Lady Day, also called the Feast of the Annunciation, the day the the archangel Gabriel appeared to the Virgin Mary and told her that she would be the mother of the son of God. (Leonardo DaVinci's portrayal of this event is shown above.) It was convenient that this day fell nine months prior to 25 December, and that nine months was the period of human gestation. It seemed logical that 25 March was the day of Mary's conception, and therefore the story told in the Gospel would take place on that date.
This became more than just a day to celebrate the Annunciation, however. Because it was treated as the start of a new year, in England it was the day that contracts between landowners and their tenant farmers would begin. If a tenant were to start farming a new plot, this was the day he would "move in." (Even as late as the 18th century in England, the tax year for Land Tax and Window Tax ran from 25 March. A proposal and investigation in 2018 about moving that date to 31 December decided to leave well enough alone.)
When the British Empire in 1752 decided—along with most of Western Europe—to switch from the Julian to Gregorian calendar, there was an adjustment of 11 days. 25 March became 5 April which was referred to as "Old Lady Day," leaving Lady Day to the (now adjusted and astronomically correct) 25 March.
Lady Day was one of the "quarter days" of the calendar, which did not exactly fall on the solstices and equinoxes. I'll talk about them next time.
