A couple weeks ago I had an online meeting with some European colleagues; I showed up in the chat room at what I thought was the agreed-upon time and they did not, which was odd, but whatever, I waited ten minutes and then rescheduled the meeting. It turns out they did the same an hour later. I’m sure you can guess why.
If you have been sent a link to this page, it is to remind you that “Eastern Standard Time” is not defined as “whatever time it is in New York City right now”, it is defined as “Eastern Time not adjusted for Daylight Saving Time“. Parts of the world in the eastern time zone that do not observe Daylight Saving Time — Panama, for instance — stay in Eastern Standard Time all year, so it is an error to assume that Eastern Standard Time and Eastern Time are the same time.
Put another way: Universal Time Coordinated (UTC) is the time in Greenwich not adjusted for British Summer Time, which is what the Brits sensibly call Daylight Saving Time. Eastern Standard Time is always UTC minus five hours, and Eastern Daylight Time is always UTC minus four hours. Eastern Time switches between EST and EDT depending on the time of year.
So when you tell someone that the meeting is at noon on Eastern Standard Time on a day in April, you are saying that the meeting is at noon Jamaican time, not noon New York City time. Since computers do what you tell them, not what you mean, you might find that setting an online intercontinental meeting for a time in “EST” might give you a different time than you think. Your best bet is to state the time in UTC, which is unambiguous.