Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
April 20 Good Friday
April 22 Easter
April 23 Easter Monday
April 27 Kingsday
May 05 Liberation Day
May 31 Feast of the Ascension
June 10 Pentecost
June 11 Pentecost Monday
December 25 Christmas
December 26 Boxing Day
DateTimeExtensions DateTimeExtensions