EST and EDT Are Different Time Zones
This year DST starts on March 14th and lasts all summer – and if you don’t remember this fact, you will one day ruin something about the time zone. So remember: Summer is daytime (EDT if you are on the East Coast) and winter is Standard Time (EST).
The same is true in other parts of the continent: Pacific Standard Time in winter and Pacific Standard Time in summer. Mountain time has MST and MDT, central time has CST and CDT. You get the idea.
Please do not schedule a virtual meeting with a foreign colleague this summer saying that you are free at such and such “EST” time. This is not the case – and if they plug Eastern Standard Time into a time zone calculator, they may end up confirming an appointment at a time that is not what you had in mind.
Fortunately, many time zone tools are smart enough to know when standard time is and when daytime is, and will correct your mistake (like this one ). But if you don’t know the difference, you are vulnerable to errors when:
- Your location has changed from standard time to daylight saving time (or vice versa), but the other person’s location has not. Switching times are not the same all over the world. For example, in the United States daylight saving time is valid from March 14 to November 7 of this year, and in the UK from March 28 to October 31. At this time, you need to be especially careful to properly perform the conversion.
- You are planning something for the future. It may be daylight saving time, but it will be standard time by the day. Better to double check if the time is displayed correctly on the calendar of everyone who comes from a different time zone.
- You are dealing with a program that ignores your ignorance. Many tools are smart enough to automatically tune, but some are not. If you select “EST” from the menu when you schedule a reminder or automatic event, but your actual time is EDT, the computer will do its job an hour later.
If you really want to remain in the dark, you can say “ET” or “Eastern Time” (similar for CT, MT, and PT); do it and you’ll just be inaccurate, you won’t go wrong. Or enter the name of the nearest city: America / New York and America / Los Angeles are options in the menu for each time zone. But if you are at a loss to specify the three-letter time zone abbreviation, make sure you know which one is which. This post was originally published in May 2018 and was updated on March 9, 2021 to change the header photo and provide additional context for 2021.