More concrete, when did we realize there was time zones and how? Not referring to the invention or regulation per se of time zones, but when did we realize there were differences in when the sun got up across the planet?
Ps. I posted this at /r/askhistory a few days with little traction, and got tipped to post it here.
hi! there's always room for people to contribute more, but meanwhile you can get started on this section in the FAQ*
Time zones and time differences
*see the link on the sidebar or the wiki tab