/etc has blocks of files with similar timestamps -- hacked?

Hi,

I'm looking around an Ubuntu box I have. In /etc I sorted by date and saw blocks of files/dirs with similar or identical timestamps on them.
In the screen shot, there are groups of files/dir with (Nov 18 and Dec 9) similar timestamps.
I know I didn't go in and touch any of those dirs on that date. Is this indication of a hacker or is it more likely just the system doing housekeeping?

Thanks
Nacht
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