Easter is linked to the Passover, which is in turn linked to the spring equinox and the first full moon thereafter. He was 33 when he died, but we don’t know for definite when he was born. There are historical events that point towards a birth date around 7BC to 4BC (the demise of Herod the Great; a comet that could have been the Star of Bethlehem; the alignment of two planets that could have been the same). But nobody really knows. And seeing as we celebrate Christ’s birth on a date nicked from a pagan festival, I don’t think it really matters.