InstantTimeZone is described as 'Freeware Program shows current time and date of different World Time Zones, as an icon in the system tray (taskbar), next to your computer clock'. There are more than 25 alternatives to InstantTimeZone for a variety of platforms, including iPhone, Windows, iPad, Online / Web-based and Android. The best alternative is World Time Buddy, which is free. Other great apps like InstantTimeZone are Time.is (Freemium), FoxClocks (Free, Open Source), Every Time Zone (Free) and Sharp World Clock (Paid).
FoxClocks is a Firefox/Thunderbird extension to display local times around the world in your status bar or any toolbar. Virtually all the worlds time zones are supported. FoxClocks also allows you to explore each time zone in Google Earth.
WorldClock shows you the time in different places over the world. Also included are the Swatch Internet Time, Julian Date and StarDate. You can also use it to synchronize the time with an atomic clock.