Retirement ages among older Americans have only recently begun to increase after their precipitous fifty-year decline. Early retirement may result from incentives provided by retirement systems; but it may also result from the rigidities imposed by market work schedules. Using the American Time Use Survey of 2003, I first examine whether additional market work is neutral with respect to the mix of non-market activities. The estimates indicate that there are fixed time costs of remaining in the labor market that alter the pattern of non-market activities, reducing leisure time and mostly increasing time devoted to household production. These costs impose a larger burden on households with lower full incomes, since wealthier households apparently purchase market substitutes that allow them to maintain the mix of non-market activities when they undertake market work. Market work also raises the set-up costs of switching among different non-market activities, thus raising the costs of generating utility-increasing variety. It also alters the daily distribution of a fixed amount of non-market activities, away from the distribution chosen when the constraint of a work schedule is not present. All these effects are mitigated by higher family income, presumably because higher-income people can purchase market substitutes that enable them to overcome the fixed time costs of market work.