ZeitRechner is a free Android app developed by Gerhard Kienlein that allows users to add and subtract time easily. The app is specifically designed for time calculations and follows the point-before-line rule, similar to a regular calculator. ZeitRechner offers the convenience of decimal format input and output, and also supports the 24-hour format.

The app's interface is simple and easy to use. Users can input time values with just a few taps on the screen. The app also supports decimal formats, making it easier for users to calculate time values. ZeitRechner is perfect for anyone who needs a quick and easy way to add or subtract time values.