Laylat al-Qadr is described in the Qur'an as better than a thousand months, and its exact date is deliberately not specified. It is sought on the odd nights of the last ten of Ramadan.

The concealment is the point: not knowing means keeping all of them. The 27th night attracts the largest crowds. Because Ramadan's start depends on a sighting that can differ between countries, the odd nights can fall on different calendar dates in different places, so the world observes the same unknown night twice.