Most people think never. I disagree. I mean, what gives you the right to stand in the way of your friend finding true love? Yeah, chances are it won't last, but it might. Here are some scenarios.

1. You broke up with your ex. Well, who are you to and try to control your friend?! YOU ended your relationship! Why should you care who your ex goes out with?!

Now, WHY you broke up with your ex may be a factor.

Did they cheat on you? Well, your friend knows that and is choosing to do something stupid (let's assume your ex cheated with somebody else). Simply tell them that it's a bad idea so you can say "I told you so" later. Then drop that fool.

Was the breakup amicable and/or mutual? Are you still friends with your ex? It's normal to feel a little hurt and miss what you had, but maturity is key on these situations.

2. I think the length of time after a breakup is important. People who have been in a relationship should wait at least as long the length of their relationship before dating somebody again. So if you were in a relationship for one year and have been broken up for two years and are basically over the person, why would it bother you that your friend wants to date them?

3. What if your friend has had feelings for your ex as long as you have, or even longer? And what if all along your ex had feelings for your friend as well but but chose you? It didn't work out. What if they're really the ones that should be together? Let your friend and your ex act on their feelings and be grateful that you weren't cheated on.

Feel free to add your thoughts and other scenarios.

U should respect that persons ex, u don't know if she still have feelings for him.which probably mean something to her. U should talk to both of them at the same time to get understanding

I think the only time it is OK to date a friend's Ex is when you want to end up being friends with NEITHER. And probably not a lot of your other friends. Sounds like a form of social suicide.

You date a friend's ex when you are ready to lose that friend. Essentially, you have to determine that dating this person is important enough to you that it is worth losing your friend, because that is a very real possibility.

Not saying it isn't possible that the person may lose a friend. But I do think that if you truly are friends, you ask that friend after some time, and really talk about it and get their blessing. Then there should be no problem at all. If friend didn't talk to friend first, then that's a betrayal of said friendship and grounds for ending the friendship.

Who are these "most people" whom "think this and that" about your decisions?

Are they possibly, all in your mind?

The right time to do any damn thing I feel like is whenever the hell I feel like it. That'd be because I self-govern and don't do anything or even want to do anything that I don't want to, all consequence and inspiration included within measure.

There is no such thing as "wrong" in personal decisions about lawful behaviour. Just plain no such thing.

You say it!

I would give a generous grace period.
7 to 10 days.

Ha!