Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
March 24 Maundy Thursday
March 25 Good Friday
March 27 Easter
March 28 Easter Monday
April 22 General Prayer Day
May 05 Feast of the Ascension
May 15 Pentecost
May 16 Pentecost Monday
December 25 Christmas
December 26 Christmas (2nd Day)