1. A first playback device comprising: one or more processors; and tangible, non-transitory computer-readable memory comprising instructions that, when executed by the one or more processors, cause the first playback device to perform functions comprising: receiving, from a second playback device, data indicating clock information of the second playback device; before receiving the data indicating the clock information, determining that data indicating an offset between a clock of the first playback device and a clock of the second playback device is not available in memory storage; determining an offset between a clock of the first playback device and a clock of the second playback device using the clock information of the second playback device storing, in the memory storage, data representing the offset; receiving, from the second playback device, a first time corresponding to audio data to be played by the first playback device as part of a synchrony group with the second playback device; retrieving, from the memory storage, the data representing the offset between the clock of the first playback device and the clock of the second playback device; determining a second time based on (i) the first time and (ii) the retrieved data representing the offset; and playing the audio data at the second time according to the clock of the first playback device.