Why is Greek Easter on a Different Date? (With a FAQ!)

"How is Greek Easter calculated?"

This is the fun one - the day is governed by these three main conditions:

It must be based on the Julian calendar, not the Gregorian one;
It must be after the Jewish holiday of Passover;
It must be on the first Sunday after the first full moon after the Spring Equinox, which for this purpose is fixed as March 21st.

Every few years, "Western" (Catholic and Protestant) Easter and Greek Orthodox Easter coincide; these years are indicated by (same) following the date.

2008 - Easter Sunday - April 27th

2009 - Easter Sunday - April 19th

2010 - Easter Sunday - April 4th (same)

2011 - Easter Sunday - April 24th (same)

2012 - Easter Sunday - April 15th

2013 - Easter Sunday - May 5th

2014 - Easter Sunday - April 20th (same)

2015 - Easter Sunday - April 12th

2016 - Easter Sunday - May 1st

2017 - Easter Sunday - April 16th (same)

2018 - Easter Sunday - April 8th

2019 - Easter Sunday - April 28th

2020 - Easter Sunday - April 19th

2021 - Easter Sunday - May 2nd

2022 - Easter Sunday - April 24th

2023 - Easter Sunday - April 16th

I got this off a FAQ travel page. It gives you the gist, and also has great pictures.