Simplify the following text for a Grade 10 native English-speaking person.
Original: The Hijra is celebrated annually on 8 Rabi ' I , about 66 days after 1 Muharram , the first day of the Muslim year ( for millions of muslims from the Sunnah Wal Jamaah sect however , the Hijra is celebrated on 1st Muharram ) .
Simplified: The Hijra is celebrated annually on 8 Rabi ' I , about 66 days after 1 Muharram , the first day of the Muslim year .