This month, Muslims around the world will commemorate Muharram or the Islamic New Year.
Muharram is one of the most important months of the year for Muslims. Its name means "forbidden," and during this month, any form of fighting or war is strictly forbidden.
Many followers will also choose to fast on its ninth and tenth days.
Here's everything you need to know about Muharram, including when it is and how it's celebrated:
What is Muharram?
The arrival of the new moon at sunset marks the beginning of the Islamic New Year.
For many Muslims, the Islamic New Year symbolises non-violence and reflection. It's common for Muslims to try to avoid negativity during this time in order to promote peace.
For Shia Muslims, it's also a period of mourning as they commemorate the martyrdom of Imam Hussain, the son of Hazart Ali and the grandson of Prophet Muhammad.
When is it?
This year, Muharram falls on 11 September and ends on 9 October.
It begins with the sighting of the new moon at sunset, which occurs on the final day of Dhu al-Hijjah, the last month of the Islamic calendar.
What date it falls on depends on the lunar cycle, upon which the Islamic calendar is based.