Yes, you were right. Switching my Windows 7 „Regional and Language Options“ to “English/UK” did the job.
Using “08/08/2013” instead of „08.08.2013“ marked the date with a color.

But unfortunally running in the UK-mode is not a useful option (having German customers).
(I observed also a problem when switching back. Also after closing the EA and re-generating the document showed me the English format of the “Last_Updated” date. I had to change/toggle the date once in the profile/requirement/conditional-formatting menu, to see the right date format in word.)

I know dealing with Microsoft internal date format can be a mess, but do you think there might be a fix in the future? Thanks.