In this article, we evaluate the impact of diminishing weekly working hours on capital operating time using the French 35‐hour working week experience. We merge the French survey on Capital Operating Time (COT, Banque de France, Central Bank of France; 1989–2004) and administrative Working Time Reduction agreements files (WTR, DARES, French Ministry of Labour; May 2003). We construct shift‐work‐based capital operating time indicators. Using differences‐in‐differences econometric models, we show that the implementation of the 35‐hour work week did not induce any reduction in COT. Hence, firms increased shift‐work to compensate for the decrease in working hours.