When did GMT start?

Could you please clarify when GMT, in the context of cryptocurrency or finance, first came into existence? I'm interested in understanding the historical timeline and perhaps the initial motivation behind its development. Is there a specific date or year that GMT was first introduced? Additionally, I'd like to know if there were any major events or milestones that preceded or accompanied its launch. Understanding the origins of GMT would help me gain a deeper insight into its current status and potential future implications in the cryptocurrency and finance industry.