As quoted by Meriam-Webster:

Main Entry: ep·och
Pronunciation: 'e-p&k, 'e-"päk, US also and British usually 'E-"päk
Function: noun
Etymology: Medieval Latin epocha, from Greek epochE cessation, fixed point, from epechein to pause, hold back, from epi- + echein to hold -- more at SCHEME
Date: 1614
1 a : an event or a time marked by an event 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
3 : an instant of time or a date selected as a point of reference (as in astronomy)
synonym see PERIOD