That's the Jewish way of counting days, based on Gen 1 (there was an evening, there was a morning).
By your calculations, Jesus would have spent 4 nights in the tomb (Wed to Thu, Thu to Fri, Fri to Sat, and Sat to Sun) instead of 3!
I think the problem is setting the year in which Jesus was crucified. By your link, if you select A.D. 34, you get Nissan 14 on a Thursday and...
Thursday Day 1
Thursday to Friday Night 1
Friday Day 2 High Sabbath
Friday to Saturday Night 2
Saturday Day 3 regular Sabath
Saturday to Sunday Night 3
It doesn't really matter, it does not affect our salvation. But it kind of makes sense, doesn't it?
OK then my year is wrong, because I wanted the high day on Thursday to make it come out right, so you say it’s 34 AD if I understand correctly?
Makes a lot of sense depending on the year. Thank you!
I was using 31 AD with Nisan 14 on Wednesday.