Just a sample site of a possible usage of DateTimeExtensions nuget package.
January 01 New Year
January 02 Day after New Year's Day
February 06 Waitangi Day
April 18 Good Friday
April 20 Easter
April 21 Easter Monday
April 25 Anzac Day
June 02 Queen's Birthday
October 27 Labour Day
December 25 Christmas
December 26 Boxing Day
DateTimeExtensions DateTimeExtensions