Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
March 27 Maundy Thursday
March 28 Good Friday
March 30 Easter
March 31 Easter Monday
April 25 General Prayer Day
May 08 Feast of the Ascension
May 18 Pentecost
May 19 Pentecost Monday
December 25 Christmas
December 26 Christmas (2nd Day)