In the year AD 638...

• The Umayyad Caliph Umar I conquers Palestine from the Byzantine Empire and invades Egpyt.
• Din Eidyn, capital of the Gododdin kingdom in what is now Scotland, falls to the Angles after a long seige and is renamed Edinburgh.
• Byzantine Emperor Heraclius publishes the Ecthesis, a statement of faith propounding Monotheletism as the official form of Christianity of the Byzantine Empire.
• Caliph Umar I inaugurates the Islamic Calendar, postdating it back to the migration of Muhammad from Mecca to Medina in 622, which becomes AH 1.
• The Dai people of China inaugurate their calendar system.
• The Kyichu Lhakhang, one of the oldest temples in Bhutan, is constructed on the orders of Tibetan King Songtsengampo.
• The first Nestorian church in China is consecrated at Chang'an by Persian monk A-lo-pen.
• Chinese pilgrim Xuanzang visits Orissa.

These people were born in 638:

• Chinese Zen master Huineng.

These people died in 638:

• Pope Honorius I, succeeded by Pope Severinus.
• Patriarch of Constantinople Sergius I.
• Patriarch of Jerusalem Sophronius.
• Chinese calligrapher Yu Shinan, author of the Beitang Shuchao ("Extracts for Books").

637 - 638 - 639

7th century