Why would different websites have different list of time zones?

Are Eastern and Atlantic not two names for the same time zone?

Oh, I see, they’re not.

I think I just illustrated how someone could get it wrong. Pacific Time means the US West Coast states. Atlantic Time some people may think is the same as Eastern Time. (Some US states are apparently considering switching to Atlantic Time… that ought to confuse even more people.)

The Atlantic provinces of Canada, and the eastern half of the Caribbean (at the Haiti / Dominican Republic divide) are on Atlantic time. Don’t know how that could possibly be confused with Eastern, considering that the Atlantic time zone is well outside the range of the continental United States, Part of Maine might extend into the general area, but not enough to confuse with whole areas that are better identified with the Atlantic timezone

Someone on whatever that website was, was just not very knowledgeable when they gave that information.

Confusing is a good word even at the best of times for me.
By the way what is the source of the 1st result in (Google search time zones USA)

Eastern Daylight Time
Time zone in Washington, DC, USA (GMT-4)
Saturday, September 7, 2019, 3:17 p.m.
2:17 p.m.
Central Daylight Time
Chicago (GMT-5)
1:17 p.m.
Mountain Daylight Time
Denver (GMT-6)
12:17 p.m.
Mountain Standard Time
Phoenix (GMT-7)
12:17 p.m.
Pacific Daylight Time
Los Angeles (GMT-7)
11:17 a.m.
Alaska Daylight Time
Anchorage (GMT-8)
9:17 a.m.
Hawaii-Aleutian Standard Time
Honolulu (GMT-10)

Who do you write to?

By the way I can see how East coast states and provinces can be mistaken as in Eastern time zone since the Atlantic is on the east. I only happen to know Eastern and Atlantic are different because I just happened to have seen the whole thing on my intro to it, on a map.

Nowhere in the continental united states is the Atlantic time zone.

So that’s why its not included in the USA time zones. Only Eastern.

As I said above, it is possible that some of the state of Maine overlaps the range of the Atlantic time zone, but Maine is all officially Eastern Standard Time.

You won’t find anyone on Atlantic time in the U.S.A. Only the Atlantic provinces of Canada (Labrador, Newfoundland, Nova Scotia, New Brunswick, Prince Edward Island)—and the outer half of the Carribean.

That’s if you happen to know all that.
It’s something that you would know only if you happen to know.

What about Puerto Rico and Virgin Islands?

They are Atlantic, also. The part of the Caribbean I was mentioning, and the only U.S. territories officially within the Atlantic zone.

But any website where it is relevant to list a time zone ought to get it right,

Does anyone know what the source of the first Google search (which I posted above and which doesn’t have Puerto Rico and Virgin Islands) is by the way?

Time Zones and Time are really interesting and really confusing. So much so that there isn’t a consistent way that all software/websites implement it. Municipalities around the world decide for themselves what time zone they will adopt and it may change over time. Add in Daylight Savings Time (DST) and it becomes an even bigger mess. Consider that when you “Fall back” the same time on the same date occurs twice—software nightmare :) And there are some countries that have 15 minute time zones. So software really has to consider Time as two things—a universal moment in time and a local perception of time.

Since time zones, in general, are subdivided into one hour slices and municipalities can decide which they adopt and whether they use DST, there are standard databases that software will use that is based on Region like TZ database and IANA. An earlier answer referred to Regions when it identified time zone as Chicago GMT-5, Denver GMT-6, etc.

So really, the short answer to your question is, it depends :)