For those who haven't heard of en_DK before, it's the "European English" (for want of a better description) locale.
It uses Commonwealth English (en_GB) for strings and ISO-14651-1 for collates.
Dates are in YYYY-MM-DD, time is in 24h HH:MM format, Monday is the first day of the week, comma is the decimal separator, currency is euro and standard paper size is A4.
Wiki sez: "[...] officially endorsed by SI/ISO 31-0 standard, as well as by the International Bureau of Weights and Measures and the International Union of Pure and Applied Chemistry (IUPAC), the American Medical Association's widely followed AMA Manual of Style, and the Metrication Board, among others."
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko