World Clock is a fantastic native app that not only makes it easy to add all the time zones you care about and shows them on a map to better help you visualize the time differences, but helps you schedule meetings across time zones too.Simple and powerful world clock:
Add cities and timezones like GMT and UTC with a few key strokes.
Convert international times with a drag of a cursor.
Schedule international calls and meetings and add them to your calendar.
Add Interactive Widget to your Notification Center
Transform your desktop with an elegant World Clock screen saver.
See weather at every location at a glance
Easily tell what time it is with clocks that change color with time of day:
– black for evening and night,
– white for morning, and
– green for working hours.
OS – MacOSX 10.7 or Later