What are some alternatives?
When comparing Sleep Time - Alarm Clock and Free Alarm Clock, you can also consider the following products
Sleep Cycle Alarm Clock - Bio-alarm clock that wakes you up at optimal times based on your sleep patterns.
Gnome Clocks - Clock application designed for GNOME 3
Sleep as Android - Common alarm clocks ignore your sleep cycles, they wake you on schedule no matter your are currently in your deep sleep. Waking up from deep sleep is unpleasant, it makes you tired and it may negatively affect your productivity during the whole day.
Talalarmo - Minimalistic android alarm
Pillow for iOS - An iOS companion that helps you sleep better 💤
KTimer - KTimer is a little tool to execute programs after some time.