epact

noun

ˈē-ˌpakt  ˈe- 

: a period added to harmonize the lunar with the solar calendar

Word History

Etymology

Middle French epacte, from Late Latin epacta, from Greek epaktē, from epagein to bring in, intercalate, from epi- + agein to drive — more at agent

First Known Use

1588, in the meaning defined above