Attached patch against roundup snap code fix the problem.
It also fix some accompanied translation problem.

After applying you need to rebuild translation file roundup.pot (in
roundup source: cd locale && gmake template). Also you may need to merge
existing translation with new roundup.pot by something like 'msgcat
--use-firest roundup.pot de.po > de_new.po'.

In your language translation filde find a pattern 
  In apropriate language file find:
"'''^
((?P<y>\d\d\d\d)([/-](?P<m>\d\d?)([/-](?P<d>\d\d?))?)? # yyyy[-mm[-dd]]
|(?P<a>\d\d?)[/-](?P<b>\d\d?))?              # or mm-dd
(?P<n>\.)?                                   # .
(((?P<H>\d?\d):(?P<M>\d\d))?(:(?P<S>\d\d?(\.\d+)?))?)?  # hh:mm:ss
(?P<o>[\d\smywd\-+]+)?                       # offset
$'''"
 and replace it to desired expression which will parse your country
specific date/time format.
  Regular expression must contain y,m,d group for full date, a,b - for
m-d variant, n for now, o for offset,H,M,S for time.
  Also translate message '.. not a date / time spec ...' from date.py to
something which describe date/time format.