I century Jewish tradition based on a lunar calendar. Ok so several decades before jesus was born Julius Caesar adopted the Egyptian solar calendar and called it the Julian calendar. The Egyptians were using this calendar for well over a thousand years and we’re the authority over the area where the Jews lived until Assyria then Babylin pushed them out.
So one can summize that maybe the Jews didn’t have a lunar calendar until after they went to Babylon and then were to change before jesus showed up to the Julian calendar. Anyway you slice it jesus the son of god died for mankind’s sins and no one knows the exact date . They instead have to use a older less accurate lunar calendar. I call bull Shiite, it’s all Astro theology related.