Hi Greenberet,
you've actually made a good catch here -- if all countries in the world are switching forward to DST during this hour.
But think about US (have done it two weeks before) or countries in the southern hemisphere (either switching back or also having different cycles like US). With respect to CET (= Central European Time) you are certainly right, and the service window Sunday 28 March 2am to 3am does not exist at all, i.e. is virtually skipped this very Sunday!
Nevertheless, I think it would be a very good idea if Configuration Templates would display either no timezone at all or at least UTC, if any. The mapping of this window to a real local time shall be driven by the local network and its configured timezone.
For networks that are configured to CET, the question for this Sunday is: Shall the Firmware Upgrade happen at 1:02am CET (= 2:02am CEST virtually) or at 2:02am CET (= 3:02am CEST) or automatically being postponed to the next Sunday when this window of lowest usage does really exist once again?
Kind Regards