The ultra- and circadian rhythms of dairy cows can be affected by environmental conditions, farm management or stress, and changes in rhythmicity might thus reflect these factors. The aim of this study was to investigate how contact with the own calf, but varying in time per day (treatments), affects the activity rhythm of dairy cows compared to cows that were separated from their calf shortly after calving (control group). The experiment was conducted for two periods in the same two dairy herds housed in a mirror-image barn. During each period, the herd consisted of control cows and cows belonging to one treatment group (either whole-day or daytime cow-calf contact for at least 90 d p.p.). The treatments were switched over the periods. The cows were fitted with accelerometers to generate actograms and calculate the Degree of Functional Coupling (DFC) of their activity. The first analysis revealed that a cow’s activity shows a typical daily structure over months and that the DFC indicates calving, estrus and separation from the calf.