Word of the Day: Epoch

ep-och / ĕp-ək, ē-pŏk
1. a date marking the beginning of a new or unique period of time
That the publication of the “Origin of the Species” marked an epoch in the development of the natural sciences is well known to the layman.
From “The Essential Dewey, Volume 1” by John Dewey, 1859 – 1952
2. a time period characterized by a distinctive development; an era
It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of light, it was the season of darkness, it was the spring of hope, it was the winter of despair. 
From “A Tale of Two Cities“ by Charles Dickens, 1812 – 1870
3. in astronomy, an instant in time by which the coordinates of a celestial body are referred
It is impossible to determine the exact epoch of this primitive celestial geography.
“Astronomy for Amateurs” by Camille Flammarion, 1842 – 1925
4. in geology, period of time during which a specific rock series is formed
Earth’s geologic epochs – time periods defined by evidence in rock layers – typically last more than three million years.  
James Owen, “New Earth Epoch Has Begun, Scientists Say” ‘National Geographic’ April 6, 2010
5. a date worth being remembered for a particular happening
But, up to that epoch of my life, I had lived in vain. 
From “The Scarlet Letter” by Nathaniel Hawthorne, 1804 – 1864