1. A first playback device of a media playback system, the first playback device comprising: one or more speakers; a network interface; one or more processors; a data storage having stored therein instructions executable by the one or more processors to cause the first playback device to perform operations comprising: receiving, via the network interface, an indication that the first playback device is calibrated; determining a time at which the first playback device was last calibrated; based on receiving the indication that the first playback device is calibrated, updating a calibration state variable to indicate that the first playback device is calibrated, and (ii) the time at which the first playback device was last calibrated, wherein the calibration state variable is stored in the data storage; and sending, via the network interface, an indication of the updated calibration state variable to a second device.