ZoneTick
ZoneTick was the former name for
Anuko World Clock software. It was developed in 2003 by
WR Consulting to show several time zones in Windows system tray. Later, this product was also known as
ZoneTick World Time Zone Clock.

ZoneTick in Windows XP taskbar showing two clocks
Why ZoneTick?
The idea for ZoneTick was quite simple - to show several clocks at once in place of the normal clock in Windows system tray area. For example, when working with someone in another time zone, the clock would show their time in addition to yours. This way, you don't need to recalculate time difference.
As ZoneTick evolved, additional features were added to it such as:
- Time synchronization.
- Desktop clocks.
- Time converter.
- Alarms and reminders.
- Skins.
- Calendar.
- Time table.
- News reader, and others.
See
Anuko World Clock for current incarnation of this software.