Why would those things have to change? We don't change them when the clocks go back (or forwards), so why would they need to change if we make one of those times permanent? Or have I just got completely the wrong idea here?
I think you missed some context. They're talking about the differences between sticking with summer time vs sticking with winter time but moving things by an hour (so a 9-5 job would be 8-4). In both cases things would happen at the same solar time.
Basically the convo was:
A: People want to change their clocks to summer time instead of changing their personal schedule
B: They don't want to change their personal time but rather society's time
A: They could just change society's schedule, it's just as easy.
C: Nah, you'd have to change a lot of things, signs, timetables, etc...
Grandparent poster was arguing that it's just as easy to change society's conventions like opening hours and business hours everywhere, as it is to change the time.
I'm saying that that is absolutely not the case, and that grandparent is delusional.
