Yes, EPOCHS is a Scrabble word!

Letter values in Scrabble US: E 1, P 3, O 1, C 3, H 4, S 1.

Is it a valid word?

EPOCHS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a period marked by distinctive character or reckoned from a fixed point or event
(astronomy) an arbitrarily fixed date that is the point in time relative to which information (as coordinates of a celestial body) is recorded
a unit of geological time that is a subdivision of a period and is itself divided into ages

Also: date of reference.