When I'm logged out, my post time is 5 hours in the future. When I'm logged in it's correct. Screenshots are from the bottom of this thread.
Logged out on top, logged in on bottom.
When you're logged out, the site doesn't know where you are, so it doesn't know what time it is there, so it shows whatever time zone the site defaults to. As far as I know, that's UTC/GMT (pick your favorite name for it), which is 5 hours ahead of the Eastern time zone.
Responding to add that this is tested on 3 devices (Ffx desktop x2, Kiwi Mobile).
[sidebar] I'm responding instead of editing my post because my images permanently transform into Loading Placeholders, when I edit a post. And .... Reuploading the image (this time) gave me some kind of metadata tag instead of the image itself. I seem to suddenly suck at internet.
That's a really odd way to do it. I can't ever recall a site that doesn't pull the zone from the browser settings (which typically pull from the system clock). The time zone settings on an authenticated site would just be for overriding browser settings.