The Devil's Birthday (Danish and Norwegian: Fandens fødselsdag) is a humorous term in Denmark and Norway referring to 11 June and 11 December.Store norske leksikon: fandens fødselsdagDen Store Danske: fanden A royal decree by King Frederick III of Denmark, issued on 17 December 1656, ordered that loan repayments and interest payments should take place on these dates.Nielsen, Oluf: Kjøbenhavns Historie og Beskrivelse 1885. Digitally available at: http://www.eremit.dk/ebog/khb/4/khb4_4.html
The term has been documented in written Danish since 1888.Det var fandens sproget.dk
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