On February 8, 1879, Sir Sandford Fleming presented two papers, “Time reckoning” and “Longitude and Time Reckoning” to the Canadian Institute in Toronto

Issued 1977

Robert Couture engraver | Will Davies designer 

… Fleming turned his gaze to the details of railway schedules, and he didn’t like what he saw. In fact, the concept of Universal Standard Time arose directly from his frustration with North American railway timetables. Every town had its own local time based on solar noon. On the face of it, this might have seemed logical, but if it was noon in Montreal then it was 11:48 a.m. in Kingston and 11:35 a.m. in Toronto. These discrepancies added up to trains that were impossible to schedule. Fleming’s solution was brilliantly simple — divide the world into 24 time zones, one for every hour of the day. It was a generalization (each zone was about 500 miles wide in middle latitudes) that paradoxically made timetables more precise.
How Sandford Fleming changed the way the world experiences time | Canadian Geographic

Remembering Sandford Fleming and Standard Time: February 8: Snapshots in History – Local History & Genealogy (typepad.com)
You can find a pdf copy of Fleming’s 1876 work Terrestrial Time here: Terrestrial Time (archive.org)