Why don't we have one timezone covering the whole earth?
And instead changing the time work and other things happens depending on where you are. Would be easier to arrange meetings across the globe. Same thing applies to summertime. You may start work earlier if you want, but dont change the clocks!
We already have it: it's called UTC. You should read about it probably, instead of asking the whole fucking world to change its uses for your convenience, shouldn't you?
My guy, instead of being condescending for no reason, perhaps you should take the time to actually understand OP's question.
OP is asking about why the world doesn't unite under one time zone (UTC+0, UTC-5, UTC+8), not time standard (UTC, TAI, GPST). The hypothetical scenario would be that midnight in the UK would be morning in Japan and evening in the US, but still considered "12 AM" by everyone in those countries, with the hope that it simplifies time coordination across the globe without having to calculate the hour offsets.
I hope you learn to be better, especially in a community called "No Stupid Questions".