I’m with you, wideawake. Jesus rose the the third day not the fourth. No small point as this is the GOSPEL, 1 Cor. 15 makes it part of the gospel message, verse four says,
1 Cor 15:4 And that he was buried, and that he rose again the third day according to the scriptures:
The answer to the three days and nights, this was a Jewish idiom. Any part of the day standing for the whole day (and night).
Here is another point. The early church fathers, without exception, said that Jesus rose on the third day, making the first day of the week to be commemorative of Jesus’ resurrection.
They would have understood Jewish idioms a lot better than these modern day interpreters. They lived almost two thousand years closer to the resurrection event than these modern day interpreters. I’d follow them before I would these modern day Sabbatarians.
That is probably the most important piece of evidence - the recognition of Sunday as the day of worship over Saturday (sabbath) early in the life of the Church. We can quibble in the 21st century over days, hours, Jewish idioms, etc - but the fact that Sunday became the day of worship is undeniable - centuries before it was cautified by later church councils.