Desperately Seeking Play Title

I am wondering if anyone can help me. I am trying to find the title of a play I read many many years ago when I was at uni. The problem being I remember very little about it except the general gist of the plot which is; A group of women discussing the fact they are having affairs and getting away with it because each of their husbands goes out religiously one night a week to various venues. It of course turns out they are having arrairs with each others husbands. I do remember that one night is obviously missing until the very end when the last woman is left on the stage and the closing line as this temptress walks out of the room is something along the lines of "I'm Monday" bringing home the twist.

If anyone has a vague incling of any play that may fit I would greatly appreciate any information.

Regards
Nicky Suckling
Stirling Players Inc