Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
March 21 Maundy Thursday
March 22 Good Friday
March 24 Easter
March 25 Easter Monday
April 19 General Prayer Day
May 02 Feast of the Ascension
May 12 Pentecost
May 13 Pentecost Monday
December 25 Christmas
December 26 Christmas (2nd Day)
DateTimeExtensions DateTimeExtensions