what does epoch means code example

Example 1: epoch

Epoch timestamp is a unit of measurement for time. It is the number of
seconds elapsed since the countdown has started. 

Beginning epochs per system:
macOS - January 1, 1904
Windows - January 1, 1601
Unix - January 1, 1970

Example 2: epochs

One Epoch is completed when a complete dataset is cycled forward and backward through the neural network or you can say your neural network has watched the entire dataset for once.