An historic period is a span of time in history that is characterized by certain events, developments, or cultural movements. An EPOCH is a longer period of time that is divided into smaller units such as centuries or millennia. An ERA is a shorter period of time that is usually defined by a particular event or development. An AGE is a period of time that is characterized by a particular set of conditions or characteristics. The Iron AGE is a period of human history that began with the use of iron tools and weapons. The Dark Ages is a period of European history that began with the fall of the Roman Empire and lasted until the beginning of the Renaissance.