Date incorrect - location correct

I noticed tonight that the date was incorrect on my Apple Watch, M1 Air, iPhone and iPad - they are all showing as 29/8/21 however my location is correct... London.

I have tried turning off "Set automatically" and can change to the correct date however when I do this and try to go to any page on the internet using Safari I get a message that Safri cannot open the page because it could not establish a secure connection.

Anyone have an idea of what could be wrong? Not sure why this has started, all devices are up to date.