In a dynamic model of large traders who manage inventory risk, we show that a daily market closure coordinates liquidity. This coordination of liquidity can improve allocative efficiency relative to 24/7 trade, fully offsetting the costs of the closure. Some length of closure is always better than 24/7 trade. A long closure is optimal in small markets with infrequent shocks, while large markets would benefit from extending trading hours to near 24/7. Our results are robust to allowing for heterogeneous information about the fundamental value of the asset. Our findings speak to proposals to modify trading hours.