Most Helpful Guy
As you read the responses below, you'll see that everyone and every relationship is different, meaning there's no definitive time table for getting over someone.
I've gotten over girls very quickly, where there was no time needed to heal (mainly because I broke it off, or it was a very amicable and mutual split), while there have been others, where like @heywhynot23 described that took a solid year or more to really have that person out of my system, where they didn't at least occupy my thoughts quite often.
The good thing, though, is the pain you're feeling goes away much faster than forgetting them completely. I mean, you can be feeling better and start dwelling on them only to find yourself feeling glum again, but that intense pain you get when you lose somebody you were really in love with is horrible at first, but subsides in a few weeks, where you can at least feel like getting out and doing things without feeling completely miserable.
I will suggest trying to date someone right away after a break with someone you really liked will not really help your suffering, and that will also be unfair to the person you start seeing. You should at least give yourself some time to process how you're feeling and just accept the fact you're sad, which is okay, because you know you won't feel like this forever and eventually you will love again.
I've rambled without giving you a specific answer, so I'm sorry, but like I mentioned, there really isn't a time table any of us can tell you. I do know the pain ends before the memory fades, eventually getting to where you'll realize you haven't thought of that person in a while, and when you do, you don't really feel the emotional reaction you used to get when his/her memory crossed your mind.
If you're going through a tough break up, then I am sorry, and hope you feel better, but trust us in knowing you will be feeling better again.1