A year is the time it takes for the Earth to complete one revolution around the sun. Specifically, this period is 365.242199 days (365 days, 5 hours, 48 minutes, 46 seconds).
Furthermore if we compare these four values ca. 1600 AD with those for the 2000 year period, (1000 AD to 3000 AD), ca. 2000 AD, using the same method, we get:
365d 5h 48m 59.6s for the March equinox. [or 365.242357 Universal days] 365d 5h 47m 56.1s for the June solstice. [or 365.241621 Universal days] 365d 5h 48m 29.1s for the September equinox. [ 365.242003 Universal days] 365d 5h 49m 30.5s for the December solstice. [ 365.242714 Universal days]