646

646 in various calendars
Gregorian calendar	646; DCXLVI
Ab urbe condita	1399
Armenian calendar	95; ԹՎ ՂԵ
Assyrian calendar	5396
Balinese saka calendar	567–568
Bengali calendar	53
Berber calendar	1596
Buddhist calendar	1190
Burmese calendar	8
Byzantine calendar	6154–6155
Chinese calendar	乙巳年 (Wood Snake); 3343 or 3136; — to —; 丙午年 (Fire Horse); 3344 or 3137
Coptic calendar	362–363
Discordian calendar	1812
Ethiopian calendar	638–639
Hebrew calendar	4406–4407
Hindu calendars
- Vikram Samvat	702–703
- Shaka Samvat	567–568
- Kali Yuga	3746–3747
Holocene calendar	10646
Iranian calendar	24–25
Islamic calendar	25–26
Japanese calendar	Taika 2; (大化２年)
Javanese calendar	537–538
Julian calendar	646; DCXLVI
Korean calendar	2979
Minguo calendar	1266 before ROC; 民前1266年
Nanakshahi calendar	−822
Seleucid era	957/958 AG
Thai solar calendar	1188–1189
Tibetan calendar	阴木蛇年; (female Wood-Snake); 772 or 391 or −381; — to —; 阳火马年; (male Fire-Horse); 773 or 392 or −380

Millennium:	1st millennium
Centuries:	6th century; 7th century ; 8th century;
Decades:	620s; 630s; 640s ; 650s; 660s;
Years:	643; 644; 645; 646 ; 647; 648; 649;

Year 646 (DCXLVI) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. The denomination 646 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Events

Arab-Byzantine War: Alexandria is recaptured by the Muslim Arabs, after a Byzantine attempt (see 645) to retake Egypt fails, ending nearly 1,000 years of rule by Greco-Roman states in the city.
Gregory the Patrician, Byzantine exarch of Africa, begins a rebellion against Constans II, and proclaims himself emperor; the revolt finds broad support among the populace.

Caliph Uthman ibn Affan founds the city of Jeddah (Saudi Arabia) on the coast of the Red Sea. He establishes a port for Muslim pilgrims making the required Hajj to Mecca.

Battle of Nikiou: The Rashidun army (15,000 men) under Amr ibn al-'As defeats a smaller Byzantine force, near the fortified town of Nikiou (Egypt).
Amr ibn al-'As builds fortifications in Alexandria and quarters a strong garrison in the vicinity, which twice a year is relieved from Upper Egypt.^[1]

Emperor Kōtoku makes a decree about the policies of building tombs. He discontinues the old customs of sacrificing people in honor of a dead man, and forbids ill-considered rituals about purgation.
A Great Reform edict changes Japan's political order. It will lead to the establishment of a centralized government with Kōtoku ruling from his palace, Naniwa Nagara-Toyosaki Palace, in Osaka.

Xuanzang completes his book Great Tang Records on the Western Regions, which later becomes one of the primary sources for the study of medieval Central Asia and India.

Muir, William (1898). The Caliphate: Its Rise, Decline, and Fall, from Original Sources (3rd ed.). London: Smith, Elder. p. 166.