Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows
Talalarmo - Minimalistic android alarm
NetTime - nettime is a time & attendance software solution.
Gnome Clocks - Clock application designed for GNOME 3