Yes it is a tricky question. The Bible says the Passover is always on the 14th Aviv
Numbers 28:16
"'On the fourteenth day of the first month the LORD's Passover is to be held.
and the Sabbath was on the 15th
John 19:31
Now it was the day of Preparation, and the next day was to be a special Sabbath. Because the Jewish leaders did not want the bodies left on the crosses during the Sabbath, they asked Pilate to have the legs broken and the bodies taken down.
And the day of first fruits was on the 16th:
Leviticus 23
Offering the Firstfruits
9The Lord said to Moses, 10“Speak to the Israelites and say to them: ‘When you enter the land I am going to give you and you reap its harvest, bring to the priest a sheaf of the first grain you harvest. 11He is to wave the sheaf before the Lord so it will be accepted on your behalf; the priest is to wave it on the day after the Sabbath.
Then how can this happen every year?
Would you like to know the answer?