Were Gregory I and Umar ibn Al-Khattāb alive at the same time?
Yes. Gregory I and Umar ibn Al-Khattāb were alive at the same time, from c. AD 586 to AD 604.
Gregory I
6th-century Roman Pope, theologian and Church Father, Catholic and Orthodox saint, 64th Bishop of Rome and Doctor of the Church
Born AD 537–543 · died 12 March AD 604