From the TED-Ed YouTube channel:
If you live in the United States, you may live in the Eastern Standard Time Zone. Or maybe you live in Mountain Standard Time or one of the other standardized time zones. But these time zones have not always been around. In fact, it’s a fairly recent development. William Heuisler explains the history of time and how trains changed everything.
Lesson by William Heuisler, animation by Flaming Medusa Studios Inc.