Just like Upjohn's review It is a great addon. Unfortunately, recently it stopped working correctly. It shows wrong time for all time zones.
In my case the hours work correctly, but minutes are frozen on :04 minutes, and never change.
[UPDATE]
Have discovered that I inadvertently created the issue by incorrectly setting a custom date and time format. Now the extension works as described.

It's a great addon, very useful one. Unfortunately, recently it stopped working correctly. It shows wrong time for all time zones.

Hours work correct, but minutes are frozen on :03 minutes, and never change.

Time zones updated. Now all my clocks are -30 minutes off real time.

Superb on Waterfox, hit and miss on Firefox 94 or later.

Waterfox still has the Status Bar, so FoxClocks sits nicely above it and works 100% of the time. In Firefox 94, however, many sites display over the top of it, so it is a bit of hit and miss (examples flashscore.co.uk, marketscreener.com). With others, on Firefox, it displays but when you scroll up (and sometimes down), it disappears (example fintel.io). It has not been updated for a year, (Oct-2020), so maybe that's the reason.

Just what i needed, great addon 5/5 , cheers!

I kept overlooking this because I was looking for a time and date extension. This has both! Thank you!

please add EST.

nice addon

I love this. I use to work in a call center and it helped me quickly reference what times were in different parts of my Country.

I would suggest an exclusion option to put URL's so that the bar does not pop up. It has caused some issues when software doesn't like the way its displayed and moved down the page a bit