Quote from Monica in The One with Phoebe's Birthday Dinner
Monica: I'm ovulating and Chandler's going to be home any minute, so I thought we would try before dinner. Phoebe: Oh. Oh, wait, does that- You guys won't be late for my dinner, will you? Monica: Believe me. Chandler and I have not seen each other in over a week. We'll probably be the first ones there.