Original sentence: Although the raid was unsuccessful, because it was customary to name a year after a major event which occurred during it, that year became known as the Year of the Elephant, which was also the year that Muhammad  was born.Later years were numbered from the Year of the Elephant, whether for the years of the pre-Islamic lunisolar calendar, the lunisolar calendar used by   Muhammad  before he forbade the intercalary month, or the first few years of the lunar calendar thus created.On the other hand, the Qur'an forbids the intercalary month (releasing the calendar from the seasons) by Sura 9, verse 36 (believed to have been revealed about the end of Muhammad's lifetime), which implies a pre-Islamic year beginning near the vernal equinox because that is when the modern lunar year began during his last year.The first day of the first month (1 Muharram) of that proleptic Islamic year, that is, after the removal of all intercalary months between the Hijra and Muhammad's prohibition of them nine years later, corresponded to July 16, 622 (the actual emigration took place in September)
Edited sentence: Although the raid was unsuccessful, because it was customary to name a year after a major event which occurred during it, that year became known as the Year of the Elephant, which was also the year that prophet Muhammad  was born.Later years were numbered from the Year of the Elephant, whether for the years of the pre-Islamic lunisolar calendar, the lunisolar calendar used by prophet  Muhammad  before he forbade the intercalary month, or the first few years of the lunar calendar thus created.On the other hand, the Qur'an forbids the intercalary month (releasing the calendar from the seasons) by Sura 9, verse 36 (believed to have been revealed about the end of the Prophet's lifetime), which implies a pre-Islamic year beginning near the vernal equinox because that is when the modern lunar year began during his last year.The first day of the first month (1 Muharram) of that proleptic Islamic year, that is, after the removal of all intercalary months between the Hijra and prophet Muhammad's  prohibition of them nine years later, corresponded to July 16, 622 (the actual emigration took place in September)