The Silver Age is one of the four Ages of the World (the others are Gold, Bronze and Iron) described at the beginning of the 'Metamorphoses' of Ovid and in the works of Hesiod.
The first age, Gold, is seen as a type of paradise, unlike those which follow, bringing with them new problems for mankind. These periods have been depicted individually, as in the work by Cranach, and also as series.
The Silver Age, according to Ovid, is one of continual springtime, a period during which people discover how to build homes, work the land, and distinguish between right and wrong. At the end of the age, according to Hesiod, the 'terrible and strong' Bronze Age men enter; this may be the moment depicted by Cranach.