The fact that you just said this, in this context, shows me how clearly embedded the AM/PM 'standard' is for people. Though that doesn't mean it's still a good idea to use it for meetings. It just signals to me that the only way of displacing this imprecise messy standard is to teach people to schedule meetings differently; and to have their smartphones display both the AM/PM time, and the standard meetings time.

Unfortunately that would probably still be as a 'timezone', and if we're doing that it may as well just be UTC since every timezone library I've every used already has that and best of all is only off by a few seconds at most without updates. (Close enough for applications that care about timezones instead of leap seconds.)