I created a time format in Drupal administration (admin/config/regional/date-time) with the following settings in EN/ DE:
DE: d. F Y -> 05. October 2016 EN: dS F Y -> 05th October 2016
The problem is that "October" is written in German like "Oktober" ("k" instead of "c"). The strange thing is that the translation works fine with every other month ("May" for example becomes "Mai" in German) but just the October is written wrong. This appears to be an issue no matter where the date field is rendered, in views or node detail page.
Additionally this seems to be an issue with the PHP date format as it the same problem when using date('d. F Y', $timestamp). Can anyone give me a hint how to solve this issue?