This study aimed to evaluate the effects of an intervention on objective working-hour characteristics. The intervention involved making modifications to the collective agreement that would limit employees' entitlement to time off as compensation. The intervention group consisted of 493 and the control group of 2,303 health and social care shift workers, respectively. We analysed the objective pay roll-based working-hour data for 2012–2013, which we obtained from employers' records, using the repeated measures mixed model. The changes in objective working-hour characteristics were small, but systematic. The intervention had some positive effects: the amount of short recovery periods (