Cronus had taken the power by mutilating his father and according to the ancient
Greeks, time started when Cronus took over.
Because Cronus had been told by his father Uranos that one of his children would take his throne, he swallowed each child his wife gave birth to, making Rhea more and more desperate. She finally wrapped a stone into a blanket and offered it to Cronus, who mistook it for a child and swallowed it immediately. The child, Zeus, she had brought up on Crete, in the holy cave Dicte, and when old enough, Zeus defeated his father and made him throw his five brother and sisters up, as well as the stone, which was taken to Delphi.
The gods then declared war against the Titans, whom they defeated and sent to the deepest cave of the underworld, Tartarus.
Cronus was one of the oldest gods worshipped by the Greeks, and his time was often referred to as the golden age. He was pictured with a sickle, and was connected to the harvest. The Athenians would celebrate him after the harvest, and the masters and slaves would be equals for a few days, joking with each other.
The Romans took over this worship, naming the festivities Saturnaliae, after the Latin name for Cronus: Saturnus.