This paper presents a distributed sleep scheduling protocol that can be used for implementing synchronous interface sleep for energy conservation in wireless Ad Hoc networks. Central ida of this protocol is to distribute a common sleep-awake cycle schedule among all nodes within a connected partition so that the nodes can turn their interface off during the sleep section of the agreed upon schedule, and they can communicate during the wake section of the schedule. By turning the interface off, the nodes can avoid idle listening consumption, which is a known reason for non-essential energy drainage in random-access network interfaces such as those running IEEE 802.11. This protocol is suited for low to moderate network loading conditions. The proposed distributed protocol employs a novel schedule synchronization technique that can work without any local time synchronization and can deliver low convergence latencies. Another notable feature of the protocol is its ability to work with unmodified existing MAC layer protocols such as 802.11. We present an ns2 based simulation model of the proposed distributed scheduling and sleep protocols for evaluating and comparing their energy performance with those of plain 802.11 MAC and a centralized scheduling mechanism. Experimental results show that with 50% wake-sleep duty cycle and 1 second wake-sleep cycle period, the protocol can achieve up to 50% energy gain within the feasible network loading situations, with a maximum packet drop rate of less than 5%.