era

noun

• a long and distinct period of history with a particular feature or characteristic:his death marked the end of an era the era of glasnost
• a system of chronology dating from a particular noteworthy event:the dawn of the Christian era
• Geology a major division of time that is a subdivision of an eon and is itself subdivided into periods:the Mesozoic era
• archaic a date or event marking the beginning of a new and distinct period of time.