KTimer is described as 'little tool to execute programs after some time'. There are more than 25 alternatives to KTimer for a variety of platforms, including Windows, Mac, Linux, Android and iPhone. The best alternative is Hourglass, which is both free and Open Source. Other great apps like KTimer are Gnome Clocks (Free, Open Source), SnapTimer (Free, Open Source), KAlarm (Free, Open Source) and Alarm Clock (applet) (Free, Open Source).
Hourglass is the most advanced simple countdown timer for Windows. Just enter a time in just about any format, and hit Enter. Pause and resume Start, stop, pause and resume your timers. Finally an app that can do everything your kitchen timer can.
All the timers I tested were too complex for my taste. I decided to write one that was dead simple, so you could run it, type in a time and hit enter. The aim of SnapTimer is to get out of the way and help you be productive.
KAlarm is a personal alarm message, command and email scheduler. You can set up alarm messages which pop up on the screen at chosen times (with sound if desired), or you can schedule commands to be executed or emails to be sent.
Alarm Clock is a fully-featured alarm clock for your GNOME panel or equivalent. It's easy to use yet powerful with support for multiple repeatable alarms, as well as snoozing and a flexible notification system.
XNote Stopwatch is a versatile and flexible multifunctional digital stopwatch / countdown timer / clock software for PC. Helpful for timekeepers at sport competitions, time tracking of work, or even as a metronome.