Thank’s to t3n I found out about Tweriod, a tool to find out the best time for sending tweets. Here are my tweets (and I do hope that the vendor takes care of local European time zone). During the week most of my followers are online in the afternoon and it seems that I do get most exposure between 3 pm and 6 pm:
At the weekend prefered time is around 5 pm. At least this seems to be the time, where most followers are online.
And last but not least … tell me why … I tweet on Mondays. 4 o’clock, Tweet time: