[GeoffR]

I think the fact that the dates are handled properly when you change the language from English to a language with a non-US date format shows that the internal representation is independent of the way the date is displayed, so I wouldn't expect any problem with server sync getting the wrong date.

It is a bit strange that during setup the firmware asks for the nearest city so it can figure out the correct timezone, and it correctly reports NZDT so it knows I am in NZ, but doesn't take the small extra step of setting the current locale to match.