I am not able to find any annotations before 2015-11-01 (this is the date of the first entry). But there have to be much more entries from the time before. I’m not sure, if my apparent first entry “deleted” all the other or if there was an update before. My piwik version is 2.16.0.
I was not able to find any annotation entries in the database, because I don’t know where to find them.