Sunni and Shi'a Muslims across the world will be observing the Day of Ashura, which marks the tenth day of Muharram, the first month of the Islamic calendar. Traditionally, Muharram is one of the four sacred months when fighting and warfare are forbidden.
The Islamic calendar is based on lunar cycles and the months begin when the first crescent of a New Moon is sighted.
This year, Muharram started on July 30 or July 31, depending on where you are in the world.
The Day of Ashura falls on the evening of Sunday, August 7 until the evening of Monday, August 8.
The day is marked by both Islamic denominations but for two different reasons. For Shi'a Muslims, the Day of Ashura is a day for mourning and commemoration of Husayn ibn Ali, the grandson of the Prophet Muhammad.
READ MORE:'Unforgivable' Drivers warned of buying fuel from 'Big 4' supermarkets
Husayn ibn Ali is believed to have been killed during the Battle of Karbala, which took place on October 10, 680 AD.
Shi'a Muslims annually commemorate his martyrdom with mourning rituals and passion plays and processions.
Preachers deliver sermons and recount the life of usayn and the history of the battle, while many take to parade the streets dressed in black hitting their chests and chanting.
Some believers also practise self-flagellation until they bleed, however, some Shi'a leaders and groups discourage the bloodletting, saying it creates a backward and negative image.
Instead, they encourage people to donate blood.
For Sunni Muslims, the day is commemorated much differently and this split stems from the differing views on the rightful successor and leader of the Muslim community following the death of the Prophet Muhammad.
The Day of Ashura is more joyful and celebrative for Sunnis, as they believe it to be the day Noah left the Ark, and Musa (Moses) and his followers were saved by Allah from the Egyptians by parting the Red Sea.
Fasting on the Day of Ashura used to be a norm in Islam as it was believed the Prophet Muhammad used to fast on this day and initially encouraged others to do the same.
DON'T MISS: 'Effective' tip to keep wasps away with 'DIY powerful repellent spray' [INSIGHT]William and Harry will 'go separate ways' as reconciliation 'doubtful' [ANALYSIS]How to clean garden furniture - DIY hacks to bring wood 'back to life' [EXPLAINED]
But later in his life, Muhammad received a revelation that caused him to make amendments to the Islamic calendar and with this, Ramadan became the official month for fasting and the obligation to fast on Ashura was dropped.
However, many carry out voluntary fasting on the Day of Ashura instead, as they believe there will be great reward if they do, according to Muslim charity Islamic Relief.
Those who do are encouraged to fast the day before and the day after for the "best and most complete fast", according to muslim.sg
According to Islamic Relief: "Fasting for the sake of Allah SWT expiates sin.
"Whilst fasting in Muharram, we should take this opportunity to make dua and renew our intentions for the year ahead."
"If you are unable to fast, reading the Qur'an or doing Dhikr can help you to feel the blessings of Muharram."