Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
April 18 Good Friday
April 20 Easter
April 21 Easter Monday
May 29 Feast of the Ascension
June 08 Pentecost
June 09 Pentecost Monday
August 31 Kingsday
December 25 Christmas
December 26 Boxing Day
DateTimeExtensions DateTimeExtensions