The video below gives a great brief explanation of the history of Easter.
This video briefly goes over the Germanic pagan roots of the term “Easter.” (The false meme about Ishtar’s connection to Easter made its way around social media again- so, hopefully this clears it up a bit for some.)
Unfortunately, the video fails to explain (in depth) that it was actually during the first ecumenical council when the specific day for the Easter celebration was designated.
The Easter Sunday date is determined based off of the vernal equinox, specifically because Passover follows the vernal equinox.However, I still think it is a great quick overview.
Today, we have Orthodox and Western-churched Christians celebrating the resurrection on the same day! The Julian and Gregorian calendars have once again converged, which means Easter lands on the same day this year!