Date format processing results in wrong dates in Dutch (and probably other languages)

We have a strange problem on 2 civicrm installations. In some cases any change to a birth date of a contact in the months march, may and october results in the date set as 1-1-1970. This occurs only in the Dutch translation, as soon as I set the language to English the problem is solved. The cause is probably that the months march, may and october are the only months where the 'M' pattern differs from English, all the other ones are the same. So I have changed the date setting from d M yyyy to dd-mm-yyyy. This means the error in the sites does not occur anymore, but the 'real' issue is still there.
I suspect this affects other languages too, and probably also the 'm' setting in the date format.