I am using 2018.2.0 for both server and desktop.
According to tableau tech support there is no solution, they closed my support ticket!!!!
The only solution I have found is to download the reports that get emailed out on a daily basis, let the extension update the dates in the work book, then reupload it to the server so it shows the correct dates when they are sent out to the consumers.
This is a total waste of my time, you would expect that if they deployed something like this, this would have been one of the first things that went into testing....what is the point of having extensions that update the dates on the server automatically, then when the subscriptions get posted out, the extensions dont run....
the time it would take me to unwind all the changes to the reports is far greater than the time needed to download, open, reupload the 30 reports on a daily basis!!!!