> as Dnm where n is 1-7 (Sun to Sat) and m is
> 1 to 5 (or -5 to -1). [...] 2011-02-D13
> would be read as the 3rd Monday in Feb. 2011
Which weekday would be day ONE: Sunday or Monday?
> The default day would be Sun.
Many weekdays have different cultural meanings. I would prefer to avoid
any default weekday if there is not any obvious agreement on it and a
really strong reason for this choice.