Doesn't do it's job well.
Should have the options to convert to a desired timezone.
Should have the ability to recognize time from various formatted strings.
Should have the ability take in date as well.

But props for being the only extension with this idea.

I'm a developer. I'm interested in contributing, if you want.

Doesn't seem to give enough information as to what it does. The only thing I see is the description on the main page of this extension is
"Converts any time zone to GMT"
Would change my review if there were detailed instructions on what the extension does.