TY - JOUR N2 - This paper examines the effect of extending the primary school day on maternal labor supply. I exploit the staggered nature of the recent German reform to extend school hours and assess whether or not gaining access to a full day school increases the likelihood that mothers enter into the labor market or extend their hours worked if already employed. I use the German Socio?Economic Panel data set (GSOEP) and link it to a self?collected school?level data set with geographical information software (GIS). Using a flexible difference?in?difference approach in the estimation of linear probability and logit models, I find that the policy has a statistically significant effect of approximately five percentage points at the extensive margin, drawing more women into the labor market. I find no significant effect of the policy at the intensive margin; women who were already working do not extend their hours worked. This has implications for policies to extend the school day that do not correspond to the working day. ID - discovery10061461 PB - WILEY TI - School Hours and Maternal Labor Supply Y1 - 2019/02/01/ AV - public EP - 151 UR - https://doi.org/10.1111/kykl.12195 SN - 1467-6435 JF - KYKLOS A1 - Shure, N SP - 118 VL - 72 IS - 1 N1 - Copyright © 2019 The Authors. Kyklos Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution?NonCommercial?NoDerivs License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits use and distribution in any medium, provided the original work is properly cited, the use is non?commercial and no modifications or adaptations are made. ER -