Month of Sundays is an idiom used to describe a very long span of time, usually referring to an extended period of boredom or inactivity. Synonyms for this phrase include "aeon," "eternity," "forever and a day," "eons," and "ages." Other similar phrases that can be used interchangeably with month of Sundays include "a lifetime," "a century," "an infinity," and "an epoch." While these phrases can be used in different contexts and situations, they all convey the idea of a seemingly unending and boring period of time. Regardless of which phrase you choose, they all refer to an extended duration of time that seems to drag on and on without end.