Robert Elz said:

Once upon a time, the world was always flat, everyone knew that,
the pope even proclaimed it...

Cite?

I doubt whether any Roman Catholic pope proclaimed the Earth flat as a matter of doctrine. That being said, flat-Earthers are still alive and kicking. We have one in California named "Mad Mike" Hughes who has said that on February 3 he will ride a steam-powered rocket that will be launched 550 meters into the air to "prove" that the world is flat.

The relevance to time zones? One argument for a flat Earth is that if the Earth really were round and orbiting the sun, we'd have to adjust our clocks twelve hours every six months to account for the fact that the Sun had gotten to the "wrong" side of the Earth, and obviously we're not doing that so the Earth cannot be round.

PS. Mad Mike is running for governor of California; the rocket is intended to launch his campaign.

McKay T. Rebuffed flat earth rocketeer says he will actually launch himself into the sky at 500 MPH this time. Gizmodo. 2018-01-25. https://gizmodo.com/rebuffed-flat-earth-rocketeer-says-he-will-actually-lau-1822364177

Riz A. Flat Earth Theory: Why don’t our clocks have to change by 12 hours in 6 months? Metabunk. 2016-01-11. https://www.metabunk.org/explained-flat-earth-theory-why-don%E2%80%99t-our-clocks-have-to-change-by-12-hours-in-6-months.t7193/