Sorry, Hatte, TI just feel that I have to write this:
The Christian Easter is celebrating the death and awakening after death of Jesus Christ. The Passover is celebrating the jews escape from Pharaoes Egypt. So far not related at all.
Yes, Jesus and his disciples celebrated Passover when he was arrested. Christianity didn't exist at this time, so no christian holiday could exist.
But the reasons that they are not occuring at the same time has also to with the catholic church desitions through time. The jewish holiday are probably more or less constant in time (you probably knows this better than me), while, after a while, it was decided that Easter Sunday should be the first sunday after full moon after the spring equinox.
And as a religious historian you should know all the facts about how the timing of the Easter holiday has changed, and you should also know about the procedure called Computus. And you should ofcourse also know about the difference in definitions through history: when Easter is after the Nicean meeting, when Easter is in the Julian calender, when Easter is in the gregorian calender.
And did you know that Denmark-Norway had their own definition of when Easter was after the year 1700 and that this wasn't changed before 1778?
In 2019, it's equinox in my part of the world March 20th at time 22:58, fullmoon occurs 4 hours later, March 21st at time 02:43. By todays rule of when Easter should occur, Easter should be March 24th, but infact Easter is 4 weeks later. The reason is that the old rule should not be taken literally, as in practical use averages and not the exact times.
As you see, there are a lot of things we need to take into consideration about the Passover and the Easter, but, allthough they are happening at the same time, it is not the same holiday.