SAVANNAH, Ga. (WSAV) – Time zones can be confusing. What do all of these letters mean? What is the difference between them? For the eastern United States, time zones can be simplified into three acronyms.

Starting off with EST, this stands for Eastern Standard Time. EST is five hours behind the Coordinated Universal Time or UTC. You will see this written out as UTC-05:00. This means that while it might be 5 a.m. on the International Space Station which follows UTC, it would be midnight in places that follow EST.

Meanwhile, Eastern Daylight Time or EDT is only four hours behind UTC. You’ll see this written out as UTC-04:00.

What does this mean? Well, if it was midnight in places following EDT, then it would be 4 a.m. on the International Space Station.

Eastern Time is simply used to tell the local time in areas that observe both Eastern Daylight Time (EDT) and Eastern Standard Time (EST). If someone asks for what time it is in ET, they’re asking what time is it in the time zones that observe EST or EDT.  

Why does all this matter?

On March 15, the U.S. Senate voted unanimously to pass legislation that would make daylight saving time permanent in most of the United States (excluding Hawaii, Arizona and some U.S. territories). This means that by the end of the year, we could stop changing the clocks altogether.

In this case, the knowledge of the difference between the types of time zones would become all the more important if you’re hoping to talk to friends from another state or country.

There are many proponents for permanent daylight saving time. The most common argument for a stop to the changing of the clocks is that changing them is more of a headache than its worth. It causes disruptions to people’s sleep cycles and their day-to-day life — something that some parents who rely on keeping regular sleep schedules for their children say is a greater issue than many realize.

To read more about the history (and the hassle) of daylight saving time, read the article linked here from the Smithsonian Magazine, which further explains why the time change started and what happened the last time Americans tried to cancel daylight saving time for good.