Klok is described as 'time zone converter widget that sits in your Today view and helps you stay on time with people you care about in different time zones. Quickly glance and convert time by swiping down from anywhere, your phone doesn't even have to be unlocked'. There are more than 25 alternatives to Klok 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 Klok 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.