The Collaborative International Dictionary of English v.0.48:

Era \E"ra\, n.; pl. Eras. [LL. aera an era, in earlier usage,
   the items of an account, counters, pl. of aes, aeris, brass,
   money. See Ore.]
   1. A fixed point of time, usually an epoch, from which a
      series of years is reckoned.
      [1913 Webster]

            The foundation of Solomon's temple is conjectured by
            Ideler to have been an era.           --R. S. Poole.
      [1913 Webster]

   2. A period of time reckoned from some particular date or
      epoch; a succession of years dating from some important
      event; as, the era of Alexander; the era of Christ, or the
      Christian era (see under Christian).
      [1913 Webster]

            The first century of our era.         --M. Arnold.
      [1913 Webster]

   3. A period of time in which a new order of things prevails;
      a signal stage of history; an epoch.
      [1913 Webster]

            Painting may truly be said to have opened the new
            era of culture.                       --J. A.
                                                  Symonds.

   Syn: Epoch; time; date; period; age; dispensation. See
        Epoch.
        [1913 Webster]

WordNet (r) 3.0 (2006):

era
    n 1: a period marked by distinctive character or reckoned from a
         fixed point or event [syn: era, epoch]
    2: a major division of geological time; an era is usually
       divided into two or more periods [syn: era, geological
       era]
    3: (baseball) a measure of a pitcher's effectiveness; calculated
       as the average number of earned runs allowed by the pitcher
       for every nine innings pitched [syn: earned run average,
       ERA]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "era":
   Bronze Age, Dark Ages, Depression Era, Golden Age, Ice Age,
   Iron Age, Jacksonian Age, Middle Ages, New Deal Era,
   Prohibition Era, Silver Age, Steel Age, Stone Age, age, days,
   epoch, glacial epoch, stage, term, time



The Jargon File (version 4.4.7, 29 Dec 2003):

era
 n.

    Syn. epoch. Webster's Unabridged makes these words almost synonymous, but
    era more often connotes a span of time rather than a point in time, whereas
    the reverse is true for epoch. The epoch usage is recommended.


The Free On-line Dictionary of Computing (30 December 2018):

ERA

   Entity-Relationship-Attribute


The Free On-line Dictionary of Computing (30 December 2018):

era

   Synonym epoch.  Webster's Unabridged makes these words
   almost synonymous, but "era" usually connotes a span of time
   rather than a point in time.