A way to make the sign of Jonah fit in 31 AD

There’ might’ be a way to make the sign of Jonah fit in 31 AD, if the first month, Nisan, followed a leap year. The Israelites used barley maturity to decide when to add the extra month; And although we can’t examine the vegetation, we know astronomically when the Spring equinox was, and that barley heads were more likely to be turning green after it. If it’s true that Jesus Christ’s crucifixion was actually in 31 AD, we’d need to apply ‘inclusive counting’ from the cross to the destruction of the 2nd temple in order for the entire long term prophetic puzzle to hold together as well as it does for 30 AD. Jesus Christ’s baptism year wouldn’t change, but the season could be later. See 4. The Countdown. (God taught us how to count inclusively with the omer in Lev. 23.)