Could they be synchronised independently?
My grandfather in France had a clock that was receiving a radio signal I think from Strasbourg.
They've been around for a while.
I remember being up late during day light hour change and i would suddenly hear the second hand rush forward.
It would stop one whole hour on the switch back.
I would use it to adjust my watch.
Nowadays I use raw GPS and any mobile phone is synced from the network anyway.
https://en.wikipedia.org/wiki/Soap_opera_effect