glibc uses for LC_ALL=de_DE the abbreviation 'Mot' for 'Mittwoch' (wednesday). I think it should be 'Mit' (the other de_* locales doing it in this way also).
Created attachment 1387 [details] Replaces 'Mot' with 'Mit'
Submitted to glibc mailing list, will probably appear on the next update
glibc-2.1.91-20 should fix this