Use python standard module to get weekdays

From @nik:

In [13]: locale.setlocale(locale.LC_ALL, "de_DE.UTF-8")
Out[13]: 'de_DE.UTF-8'

In [14]: list(enumerate(calendar.day_name))
Out[14]: 
[(0, 'Montag'),
 (1, 'Dienstag'),
 (2, 'Mittwoch'),
 (3, 'Donnerstag'),
 (4, 'Freitag'),
 (5, 'Samstag'),
 (6, 'Sonntag')]

In [18]: list(enumerate(calendar.day_abbr))
Out[18]: [(0, 'Mo'), (1, 'Di'), (2, 'Mi'), (3, 'Do'), (4, 'Fr'), (5, 'Sa'), (6, 'So')]