FoxClocks shows times around the world – or just your local time – at the bottom of your browser. It deals with daylight saving time so you don’t have to.
Here are more details about the add-on from the developers:
FoxClocks lets you keep an eye on the time around the world – or just your local time – by putting small clocks in your statusbar. Choose from a set of useful time formats or create your own – custom formats are easy to create and very flexible.
You can set each clock’s colour, or even have a clock change colour during certain hours (perhaps green when it’s a good time to Skype your friends in Japan). Too much stuff in your statusbar? Move your clocks to a toolbar, or switch to ‘icon’ mode and hover over the FoxClocks icon to see your clocks.
Want to learn more about FoxClocks? Find out about it on the Firefox Add-ons website.