Nisan 14 was preparation and crucifixion [Leviticus 23:5] Wednesday. Placed in tomb at sunset Wednesday/Thursday [Luke 23:53-54]. First 24 hours in tomb; Wednesday evening/ Thursday (the 15th) and first Sabbath of Unleavened Bread begins [Leviticus 23:6]. Second 24 hour period in tomb; Thursday evening/Friday (the 16th) and the count of the Omer begins [Leviticus 23:15]. Third 24 hour period in tomb; Friday evening/Saturday and resurrection before sunset on the Sabbath [Matthew 28:1][Luke 24:1][John 20:1].
The reason the mainstream church selected 33 A.D. was to allow their 1 1/2 day theory of Friday crucifixion/Sunday resurrection to workout. Passover fell on a Friday that year.....but 72 hours later (per scripture) would put the resurrection on Monday afternoon....at sunset.