The next upcoming Laylat al Qadr starts on sundown of May 31 ending at sundown on Saturday June 1st, 2019. Laylat al Qadr is a day that observes the night when the Prophet Mohammad received the first versus of the Koran.
Many Muslims during the day will refrain from drinking, eating and other pleasure seeking activities. They will also spend the day time praying and reading from the Koran. During the evening Muslims will eat and drink and spend time in the mosque or community centers in a time of togetherness and worship in celebration of Islam.
It is guessed that Mohammed received his first versus of the Koran from God around 610 CE with Laylat al Qadr marking the day of this anniversary.