A period of history is a span of time in which certain events occurred. An EPOCH is a longer period of time, usually lasting millions of years. An ERA is a shorter period of time, usually lasting hundreds or thousands of years. An AGE is a period of time that is characterized by certain features or events. The Iron AGE is a period of history that began around 1200 BC and lasted until the end of the classical period in the Mediterranean region. The Stone AGE is a period of prehistory that began around 3.3 million years ago and ended around 3000 BC.