In
http://www.worldtimeserver.com you can easyly convert one time from one timezone to another and see the current time everywhere in the world. Maybe you can use Plus' quick texts to launch a browser with the page of the site you want to look. For example, a quick text with the text
/run
http://www.worldtimeserver.com/time.aspx?locationid=ES
would show the time in spain. And if you change ES by (!P) you can put the code of the country you want.
I think that's a better solution than coding a plugin, imo. It can also be put in a tab.
Looking for a 'world time clock' plugin
/ 
