NodaTime has AnnualDate that can be used to represent a date for recurring events, e.g. birth dates or anniversaries. AnnualDate does, however, require that the date is the same each year.
Is there a way to specify an annual date in relative terms, such as "the first Sunday in June", "the second to last Monday in January", "the Sunday before May 3rd", or "the third Wednesday in September"? This would be beneficial for things like movable holidays and such.