Chronos-Fit is a program for detection of rhythmic organisation in arbitrary data, which are recorded over a period in time. Originally it was developed for the evaluation of Ambulatory Blood Pressure Monitoring (ABPM) data. However, it has now been expanded to other fields of rhythm research: e.g. measurements of activity in humans, radiotelemetric data of blood pressure, heart rate, activity, temperature etc. in animals and data collected otherwise around the clock. Now it can process any type of data. The program performs a Linear Analysis and a Rhythm Analysis. Linear Analysis consists of conventional parameters like Mean, Standard deviation and AUC. Rhythm Analysis performs a partial Fourier analysis of the data. Moreover, modules for group analysis, power spectrum analysis and actograms are implemented.