If you ever need to schedule an online meeting or a conference call with your co-workers who are located in different cities and countries, EveryTimeZone.com should come handy.
In Every Time Zone, you just have to drag the green bar to see the corresponding time (and date) in the different time zones of the world. The shades of blue indicate the hours of the day and the lighter the shade, the more suitable that time would be for the meeting for colleagues located in that particular time zone. The app works offline too.
TimeZen.com is another useful web app for finding a common meeting time across multiple timezones. While Every Time Zone provides the world time at a glance, Time Zen lets you pick cities where your colleagues are located.
To get started, add one or more cities to the list and then move the slider to see the time across each of these cities. The green area on the slider represents the time when all the selected cities are in the time range of 8am - 10pm which is generally considered a good time for a global meeting /conference call.
Related: Online World Time Clocks