We analyze the relationship between temporal flexibility at work (i.e., the ability to vary or change the time of beginning or ending work) and the motherhood wage gap of working parents, in the US. To that end, we first characterize temporal flexibility at work using the 2017-2018 Leave and Job Flexibilities (LJF) Module of the American Time Use Survey, which contains self-reported information on temporal flexibility at work. We find cross-occupation differences in the ability to vary or change work-times, with more than 70% of full-time workers having flexibility, in occupations such as computer and mathematical science, management, architecture, and engineering. Less than 40% of full-time workers in construction and extraction, education, training and library, or production have temporal flexibility at work. We examine the temporal flexibility of the gender gap among full-time working parents, using the American Time Use Survey for the years 2003-2019. Our analysis reveals that temporal flexibility has a U-shaped relationship with the wage rates of both fathers and mothers, and that temporal flexibility has a concave relationship with the motherhood wage gap, with a maximum being reached at the level of 55% of temporal flexibility. Our analysis of the structure of work hours reveals that temporal flexibility is reflected in how work hours are structured throughout the working day, and also serves as evidence that our measure of temporal flexibility captures the technologies of production, rather than the characteristics or motivations of a given company policy. This paper posits temporal flexibility as a factor affecting the motherhood wage gap.