Calendar and file manager partly in German

Ubuntu 14.10, installed in English, with Belgian keyboard. No additional languages installed.

Everything is displayed in English as expected but some parts appear in German: the calendar and the dates in the file manager.

I have no idea how it got there, and how to get rid of it.

This is controlled by the Regional Formats setting in Language Support. Based on your time zone choice during installation, the installer 'guessed' that you prefer the Belgian conventions for time/date, currency, etc., so currently you probably have Deutch (Belgien) selected in the Regional Formats tab. Unfortunately (which is a bug) it means that the weekday and month names are showed in German.

The simplest way to change it is to switch to some of the English options in Regional Formats. Often English (Denmark) is a suitable choice in Europe.

Another option is to edit your ~/.profile file, and add the line

export LC_TIME=en_DK.UTF-8

That will fix the weekday and month names, without affecting things like currency and number formats.