Or, Oester, or....
Before Easter was coopted as the time Jesus ascension, there were a number of cultures going back as far as 7000 years before Jesus, that celebrated the equinox. Ishtar of Sumaria is one, Oester of Scandinavia is another. Not to say that these celebrations were the true Easter, but are shared at the same time as the Christian celebration. It seems that it was coincidental or a decision to leverage an already practiced holiday on the part of Roman Emperor's Council of Nicea when it issued the Easter Rule, which states that Easter shall be celebrated on the first Sunday that occurs after the first full moon on or after the vernal equinox.