Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
March 23 Easter
March 24 Easter Monday
May 01 LabourDay
May 11 Pentecost
May 12 Pentecost Monday
July 21 Belgium_NationalHoliday
August 15 Assumption
November 01 All Saints
November 11 Armistice
December 25 Christmas
DateTimeExtensions DateTimeExtensions