The Islamic new year, or the Hijri new year, marks the start of the Muslim lunar calendar.
The calendar has been observed for more than 1,440 years and is used to date important Muslim events including the beginning of Ramadan (month of fasting), Eid al-Fitr and the start of the Hajj pilgrimage.
The Islamic new year starts with the migration, also known as the Hijrah, of Prophet Muhammad and his companions from Mecca to Medina in 622 AD, after they were repeatedly persecuted and threatened.
The Hijrah, considered one the most important events is Islamic history was chosen as the starting point for the calendar in 639 AD by Umar ibn al-Khattab, the second caliph.
Sourced from https://www.aljazeera.com/news/2021/8/6/islamic-new-year-what-you-need-to-know