in a month of Sundays

in a month of Sundays

At any point; under any circumstances. Used in the negative to convey that something will never happen. Not in a month of Sundays did I think that I would actually win the lottery! A: "Do you think Samantha will agree to go on a date with Jake?" B: "Not in a month of Sundays!"
See also: month, of, Sundays
References in classic literature ?
I ain't seen so many black eyes and bloody noses in a month of Sundays.
What it was doesn't much matter, but no outsider would have found those keys in a month of Sundays.