Cycle
From Tardis Wiki, the free Doctor Who reference
A cycle was a unit of time used by several species, including the Sontarans, (COMIC: Pureblood) the Cybermen, (AUDIO: Hour of the Cybermen) and the Sensorites. (AUDIO: Sphere of Influence)
Thals used cycles as well, with "fifty cycles" being many decades, spanning four generations. (AUDIO: Return to Skaro)