The majority of Islamic nations observe this day as a public holiday. Muharram is to befall on 29-30 July worldwide marking the islamic new year 1444.
The Hijrah, the Prophet’s travel from Mecca to Medina on the first of Muharram in 622 CE, marks the beginning of the Islamic calendar year, marking the beginning of the Muslim era.
The Prophet then proclaimed in the Constitution of Medina that Muslims are a universal brotherhood with a distinct identity in faith and philosophy after the Hijrah.
Afterward, Hijrah was chosen as the starting point for the Islamic calendar by Umar ibn Al-Khattab, a close friend of the Prophet Muhammad and the second caliph, perhaps in 638 or 639 CE.
Either astronomical calculations are used to predict future dates for the Islamic calendar. Or the month is determined by local moon sightings.
Muharram is marked by remembering the Martyrdom of Hazrat Hussain, the Prophet Muhammad’s grandson who perished at the Battle of Karbala in 680 AD on 10th Day of Muharram