I believe there is a right time to start dating again after a break-up, but the specific "time" can be individual. To know if you are ready to start dating again, there are some questions you should ask yourself:
Do you still think of your ex first thing each day? - if your ex is only a fleeting thought every now and then and not the first thought of each day, you are probably ready to start dating again.
Do you find yourself talking about your ex a lot? - You're recovering well if your ex isn't the topic of most conversations. During the recovery period, we tend to talk about the ex every chance we get. This is a way of processing what has happened. When you no longer feel the need to talk about the ex, you are releasing them from your system.
"Our song" - Many couples have an "our" song. After a break-up, hearing that song can bring back fond memories, although not a lot of sadness. If you can hear the song you once shared and not reach for the Kleenex, you may be ready to move on to someone new.
The phone call - if your ex calls, ...