The night, also known as the Night of Destiny, is described in the Quran as being “better than a thousand months” (97:3).
It is believed to be the night when the Quran was first sent down from Heaven to the world and also the night when the first verses of the Quran were revealed to Prophet Muhammad (Peace Be Upon Him).
The specific date of Laylat al-Qadr is not mentioned in the Quran. Shia Muslims believe that Laylat al-Qadr is to be found in the last ten odd nights of Ramadan but mostly on the 19th, 21st or 23rd of Ramadan with 23rd being the most important night.