Oh man, don't get me started. The 3 _calendar_ month notice that needs to be sent in writing (or faxed) is so ridiculous and I wonder if it is done to make it more difficult to get out of contracts. In my case, I had no idea that the written notice receive date matters (unlike the US, where you typically use the postmark date), due to mail delay because of a holiday my notice arrived 2 days late and that was enough to make them pay for another month despite there being an incredible amount of demand in Berlin for apartments.