The Quran was revealed on Laylat al-Qadr (The Night of Power), which falls in the last ten nights of Ramadan, most likely the 27th night. This night is described in Surah Al-Qadr as 'better than a thousand months.' The entire Quran was sent down from Lauh al-Mahfuz to the lowest heaven on this night, then revealed gradually to the Prophet over 23 years.