Thank you for the the reply and your envolvement. Unfortunately I was unable to make it work with the provided sollutions.
When I try Craigs option: echo date_format($productdate,“Y/m/d”); It returns: “date_format() expects parameter 1 to be DateTimeInterface”. Somehow it seems that the returned getData is converted into a string value (var_dump confirmes this).
Then I tried Thomas’s alternatives, putting the javascript at the bottom of my script at: Magento_Sales\templates\email\items\order\default.phtml, but it didn’t change the output.
When I try the second option I get an error that the variable is undefined, I suspect it also has something to do with the data returned as string instead of datetime.