Vernal equinox, eh?
When do the Jews say Passover is each year?
You would have to ask them; I don’t know.
The Passover begins on the 15th day of the month of Nisan, which typically falls in March or April of the Gregorian calendar. The 15th day begins in the evening, after the 14th day, and the seder meal is eaten that evening. Passover is a spring festival, so the 15th day of Nisan typically begins on the night of a full moon after the northern vernal equinox.[34] However, due to leap months falling after the vernal equinox, Passover sometimes starts on the second full moon after vernal equinox, as in 2016.