1. Why do we have a day off tomorrow?

2. Isra and Mi'raj
Known as the The Prophet's Ascension or the Night Journey, this holiday is observed on the 27th day of Rajab, the seventh month in the Islamic calendar.
Isra and Mi’raj marks the Prophet Muhammad’s (PBUH) journey from Mecca to Jerusalem sometime around the year 621, according to Islamic belief.

3. The journey to Jerusalem is known as 'Isra'.
The second part of the journey is know as the Mi'raj, which means ladder in Arabic – this was when Muhammad (PBUH) was told how many daily prayers should be said (five) which is why it is the duty of a Muslim to pray five times daily.
Celebration of Isra and Mi'raj include prayers during the night tonight and many Muslim cities will keep their lights on all night.