There are numerous ahadeeth which have come from the Messenger of Allaah (sallahAllaahu alayhi wasallam) regarding when this great night is , and the conclusion is that it is in the last ten days [the days we are in now!!], as for exactly when?
Then there is no specific night. But most likely in the odd nights. Especially the last seven nights. But it can even be the 21st night, [which is tomorrow night], as it did happen once during the time of the Messenger of Allaah (sallahAllaahu alayhi wasallam).
The point is: we need to strive for this great night in each of the remaining nights. Look at the great excellence:
Abu Huraira (may Allaah be pleased with him) said: the Messenger of Allaah (sallahAllaahu alayhi wasallam) said: “Whoever fasts Ramadhan eemanan [truly believing in its obligation and fulfiling it as a command of his Lord], and ihtisaban [doing it sincerely for Allaah and hoping for the reward from Him]: then all of his previous sins are forgiven.
And whoever stands in Laylatul Qadr eemanan and ihtisaban all of his previous sins are fogiven.” 
Abu Huraira (may Allaah be pleased with him) said: When Ramadhaan came, the Messenger of Allaah (sallahAllaahu alayhi wasallam) said: “The month of Ramadhan has come to you, a blessed month, Allaah has made obligatory on you fasting it, in it the doors of Paradise are opened and the the doors of hell are closed, and the devils are tied, in it is a night better than a thousand months, the one who is prevented from its virtue; then he has really been prevented from good.” 
With all the sins we commit, all the shortcomings we have in fulfilling our obligations: it is upon us to strive these ten nights so that we can achieve the great excellence of Laylatul Qadr.
The night wherein worshipping in it is equal to worship in a 1000 months!
SubhanaAllaah, how merciful is this Lord!
O Allaah, aid us.
1. Agreed upon
2. Ahmad, and An-Nasa’ee, Shaykh Albaanee said it is Authentic by other supporting narrations: Saheeh Targheeb: 999