> It may or may not be local time in London, but it's unambiguous.
True, but unfortunately humans only care about local time. Setting a meeting for "6PM London time" is how pretty much the entire world operates. If your app can't deal with that, your app is doing it wrong. The world doesn't care that it isn't "well-defined", as developers we just have to deal with it.
> Thus proving that what you want does not exist and cannot exist.
But it does exist, and many calendar apps operate exactly like that. It just requires them to update their timezone database every few months - which in many cases already happens automatically as part of OS updates.
"2030-07-01T18:00:00+01:00" conveys no more information than "2030-07-01T17:00:00Z". The UTC offset is meaningless because it is impossible to get a timezone from it, so it cannot be fixed in the future. It essentially screams "we tried to do local time and failed".
True, but unfortunately humans only care about local time. Setting a meeting for "6PM London time" is how pretty much the entire world operates. If your app can't deal with that, your app is doing it wrong. The world doesn't care that it isn't "well-defined", as developers we just have to deal with it.
> Thus proving that what you want does not exist and cannot exist.
But it does exist, and many calendar apps operate exactly like that. It just requires them to update their timezone database every few months - which in many cases already happens automatically as part of OS updates.
"2030-07-01T18:00:00+01:00" conveys no more information than "2030-07-01T17:00:00Z". The UTC offset is meaningless because it is impossible to get a timezone from it, so it cannot be fixed in the future. It essentially screams "we tried to do local time and failed".