epoch

\EP-uk\ noun
1 a : an event or a time that begins a new period or development b : a memorable event or date
2 *a : an extended period of time usually characterized by a distinctive development or by a memorable series of events b : a division of geologic time less than a period and greater than an age

Example sentence:
The Victorian epoch is often seen as a time of great formality.

Did you know?
"Epoch" comes to us, via Medieval Latin, from Greek "epoche," meaning "cessation" or "fixed point." "Epoche," in turn, comes from the Greek verb "epechein," meaning "to pause" or "to hold back." When "epoch" was first borrowed into English, it referred to the fixed point used to mark the beginning of a system of chronology. That sense is now obsolete, but today "epoch" is used in some fields (such as astronomy) with the meaning "an instant of time or a date selected as a point of reference." The "an event or a time that begins a new period or development" sense first appeared in print in the early 17th century, and "epoch" has been applied to defining moments or periods of time ever since.