The Jews didn’t have names for the days of the week, so they counted.
“One of the Sabbath” ( or “one of the Sabbaths,” perhaps because the the weekly Sabbath fell on the same day as a yearly Sabbath that year ) would be Sunday, “two of the Sabbath” would be Monday, etc.
There’s also the typology of the wave sheaf offering to consider ( on the morrow after the Sabbath, during the Feast of Unleavened Bread, you shall offer the first of the first fruits. )
And the statement of the disciples on the road to Emmaus ( today is the third day. )
It also seems obvious that the empty tomb was discovered in the morning, and if Jesus had “not yet ascended to the Father,” it seems strange that He should be walking the earth ( and appearing to no one ) all night.
And I think “one of the Sabbaths” is used in a passage in the book of Acts, in a context that would place it after Pentecost ( making it impossible to restrict the meaning to one of the two Sabbaths of Unleavened Bread. )
BTW: There are various ways ( based on idiomatic ussage ) to explain the phrase “three days and three nights,” but I personally lean toward a Thursday Crucifixion ( as did Bishop Westcott.)
Different Jewish sects may have observed the Passover Sedar at different times ( sundown on the 13th, or sundown on the 14th–depending on how they interpreted a Hebrew phrase ), and this could explain a lot.