Nissan 14 is always the first full moon after the spring equinox.
Not on the Jewish calendar, Duran. I'm a Jew.
There are 30 days to a Jewish month. Each month is Lunar. The middle of each month is the 15th. That is the day of the full moon.
Passover 2025: NISAN 15
While it is true that Jewish Scripture say that we are to "observe the festival of Passover" beginning on the "14th day of the month," that is because we begin doing that much like Christians begin observing Christmas on Christmas Eve, not on December 25th but on the 24th of December.
On the 14th day of Nisan all the leaven in Jewish homes is to be gotten rid of, either by eating and using up, selling, giving away, or burning it. Back in the days of the Temple, at 3 pm, the priests began slaughtering all the lambs, thousands of them, for the Seder meals, as that was the only way to get a kosher lamb for your plate in those days. Josephus said that in 70 CE he counted 256,500 Korban Pesach (kosher lambs) prepared by sundown, the 15th of Nisan, the beginning of Passover. In 65 CE, Josephus claimed there were “not less than three million” that had gathered for the celebration.(Josephus, Wars, 2:280) Yet as Josephus, the Talmud, and all other historical records verify, the Jews have always observed the 14th of Nisan as Preparation Day and Nisan 15 as the 1st day of Passover.
Use AI and ask if the Jews changed the date and you will see that this never happened. That is a Watchtower belief. It has always been on Nisan 15. The 14th is the eve, the day to prepare.