Compared to other industrialized countries maternal labor supply in Germany is low, i.e. in terms of participation and because a large share of mothers is working parttime.An important determinant of maternal labor supply is the availability of childcare including all-day schools, which are planned to be expanded further in the recent coalition agreement 2018.By using regional variation in the supply with all-day schools to identify their causal effect on maternal labor supply this project contributes to the public debate in Germany as well as to existing literature on maternal labor supply and the effects of public childcare.