I know, and it gives you an extra night in the tomb plus a day for the women to visit the tomb before Sunday. That’s why I don’t think 31 AD is the year.
I agree that it does not matter for sake of argument, as we have our salvation.
However there are several things that had to be fulfilled Biblically and here is one explanation that says it can only be 31 AD.
http://www.4angelspublications.com/Books/GCC/Chapter%205.pdf