I have been messing around with some add-ons (added/removed them) and I suppose(?) something has been re-set somewhere, somehow, I don't know, but fact is that files that are downloaded are now having the date-time stamp from the server, not the download time stamp.
Vainly tried to find a related item in the advanced settings.
How to get the previous situation back?
i.e. files that are downloaded are getting a modified date-time stamp of download.