Answer By Dr Zakir Naik,The reason that one can think of that why Allah (Subhanahu wa Ta'ala) concealed the exact date or day of the night of Lailatul Qadr. The first that we can think of is because Allah (Subhanahu wa Ta'ala) wants us to double our effort, so that we can pray more, we can worship him more, that's the main reason. If the exact date was known then would have only done on that day. Number two and the reason Allah (Subhanahu wa Ta'ala) concealed is because, so that he can make out who are the serious believers and the non serious believers. A serious believer will really see to it that he does not miss the Lailatul Qadr and he will try and worship in the last ten nights of Ramadhaan. And furthermore he would even try to seek and stay awake late in the night, till early parts of dawn, so differentiate between the serious and the non serious believer. Furthermore Allah (Subhanahu wa Ta'ala) in this manner conceals many things for example, Allah (Subhanahu wa Ta'ala) says that the prayer, the Du'a, the supplication done on Friday will be accepted, but does not tell the exact time. So a person does more supplication throughout the day of Friday. Further it's mentioned in Sahih Bukhari, Vol No. 3, (Book of Conditions), Hadith No. 2736, our beloved Prophet Muhammad (Sallallahu alaihe wa sallam) said, that "Allah has 99 names, hundred minus one, and whoever knows these names he will enter paradise." But Allah (Subhanahu wa Ta'ala) and the Prophet did not mention these exact 99 names so that we mention as many names of Allah (Subhanahu wa Ta'ala) as possible and try to memorize them. And did not reveal which is the greatest name of Allah (Subhanahu wa Ta'ala) so that we mention all the names of Allah (Subhanahu wa Ta'ala). Further Allah (Subhanahu wa Ta'ala) has not mentioned the names of all the Awliyas, the friends of Allah (Subhanahu wa Ta'ala), he has mentioned many in the Qur'an and the Hadith, but not all of them, so that we respect all the believers of the past. Furthermore Allah (Subhanahu wa Ta'ala) has not told us which day will we die, if we had know that, that we are going to die after may be 50 years, so he will say lets enjoy our life now, over 50 years is left and may be I'll repent in the last few years, we don't know when we are going to die. So we should be prepared that if we die now, our account should be in the positive and try and be prepared for the Day of Judgment. So we don't know when we are going to die. So a person is always doing good deeds... Maximum as far as possible. And furthermore Allah also hasn't revealed when is the hour, when is the day of judgment as Allah says in Surah Luqmaan, Chapter No. 31, Verse No. 34, that "No one knows the hour, when will it come." So that we are prepared to die today, prepared for the day of judgment so that we should always be following the commandments of Allah (Subhanahu wa Ta'ala), so that's the reason Allah (Subhanahu wa Ta'ala) has not given the exact day and date of Lailatul Qadr