photo source: UK Parliament
March 24, 1603: death of Queen Elizabeth
March 25: Lady Day
One of the absolutely "crucial fixed dates" of the Tudor calendar was Lady Day, March 25th. Named for the Virgin Mary, it was the Feast of the Annunciation, the start of a nine-month countdown to Christmas and therefore a fresh start to the familiar pageant of salvation. It was also the day to pay rents and sign contracts, and the day the secular year changed: Queen Elizabeth, dying the day before Lady Day, would be considered by her contempraries to have died on the last day of 1602. In London, Lady Day also marked the end of the first sitting of the Westminster Courts for the year -- official business had been conducted since January 13th -- and the beginning of a vacation which would last until Easter Term, when the courts next sat commencing on the fifteenth day after Easter.
David Cressy, Bonfires and Bells: National Memory and the Protestant Calendar in Elizabethan and Stuart England. Berkeley and Los Angeles: University of California Press, 1989, p. 20 ("crucial fixed date"), pp. 10-11 (secular year, Westminster calendar).