A cycle was a unit of time used by several species, including the Sontarans, (COMIC: Pureblood) Chelonians, (PROSE: Zamper) and the Sensorites. (AUDIO: Sphere of Influence)
The Cybermen also measured time in cycles. (AUDIO: Hour of the Cybermen) During the Great Cyber War, the Super Controller stated that at the current rate of attrition, Cyber-operations on Telos would become untenable in 2.55 cycles, then he would cease to function. (AUDIO: Last of the Cybermen)
For Thals, "fifty cycles" was many decades, spanning four generations. (AUDIO: Return to Skaro)
Ice Warriors used "cycle" as well as "solar cycle," along with hours. (AUDIO: The Ordeal of Peladon)