English
exasecond
From exa- + second.
Today it means
noun An SI unit of time equal to 10¹⁸ seconds. Symbol: Es. (= 31 709 800 000 years, which is more time than has elapsed in the Universe, that is, since the Big Bang [about 13 800 000 000 years].)
Language periods are conventional ranges, not dates for this word.
Etymograph / exasecond