Zones is described as 'is the simplest way to convert time zones between cities around the world. Recently rewritten and updated to version 2.0, Zones is the best way to deal with time zones on iPhone and iPad'. There are more than 25 alternatives to Zones for a variety of platforms, including Online / Web-based, Windows, iPhone, iPad and Android. The best alternative is timeanddate.com, which is free. Other great apps like Zones are World Time Buddy (Freemium), Time.is (Freemium), timee.io (Free) and FoxClocks (Free, Open Source).
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.