644

644 in various calendars
Gregorian calendar	644; DCXLIV
Ab urbe condita	1397
Armenian calendar	93; ԹՎ ՂԳ
Assyrian calendar	5394
Balinese saka calendar	565–566
Bengali calendar	51
Berber calendar	1594
Buddhist calendar	1188
Burmese calendar	6
Byzantine calendar	6152–6153
Chinese calendar	癸卯年 (Water Rabbit); 3341 or 3134; — to —; 甲辰年 (Wood Dragon); 3342 or 3135
Coptic calendar	360–361
Discordian calendar	1810
Ethiopian calendar	636–637
Hebrew calendar	4404–4405
Hindu calendars
- Vikram Samvat	700–701
- Shaka Samvat	565–566
- Kali Yuga	3744–3745
Holocene calendar	10644
Iranian calendar	22–23
Islamic calendar	23–24
Japanese calendar	N/A
Javanese calendar	535–536
Julian calendar	644; DCXLIV
Korean calendar	2977
Minguo calendar	1268 before ROC; 民前1268年
Nanakshahi calendar	−824
Seleucid era	955/956 AG
Thai solar calendar	1186–1187
Tibetan calendar	阴水兔年; (female Water-Rabbit); 770 or 389 or −383; — to —; 阳木龙年; (male Wood-Dragon); 771 or 390 or −382

Millennium:	1st millennium
Centuries:	6th century; 7th century ; 8th century;
Decades:	620s; 630s; 640s ; 650s; 660s;
Years:	641; 642; 643; 644 ; 645; 646; 647;

Year 644 (DCXLIV) was a leap year starting on Thursday (link will display the full calendar) of the Julian calendar. The denomination 644 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

Emperor Taizong of the Tang dynasty sends a Chinese expeditionary force, to invade and annex the Tarim Basin kingdom of Karasahr in Xinjiang, a vassal of the Western Turkic Khaganate. The oasis state is conquered, and Western Turks sent to assist Karasahr are defeated by the Tang forces.^[1]
Zenkoji, a Buddhist temple and landmark spot in Nagano, Japan, is officially built by Empress Kogyoku.^{[citation needed]}

Oswine, son of the late king Osric of Deira, manages to establish himself as king of Deira (Northern England) despite armed objections from King Oswiu of Bernicia. His succession, probably the choice of the people of Deira, splits the Kingdom of Northumbria.^[2]

Valentinus, Byzantine general, attempts to usurp the throne of his son-in-law Constans II. He appears at the gates of Constantinople with a contingent of Byzantine troops, and demands to be crowned emperor. His claim is rejected, and Valentinus is lynched by the populace.^[3]

November 3 – The second caliph Umar, r. 634–644, dies of wounds inflicted by the Persian slave Abu Lu'lu'a Firuz at Medina. On his death bed he appoints a committee to determine his successor. They select Uthman ibn Affan, who becomes the third caliph of the Rashidun Caliphate.

^ Wechsler, Howard J. (1979). "T'ai-tsung (reign 626–49) the consolidator". In Twitchett, Dennis (ed.). The Cambridge History of China, Volume 3: Sui and T'ang China, 589–906, Part I. Cambridge: Cambridge University Press. p. 226. ISBN 978-0-521-21446-9.
^ Parker, Anselm. "St. Oswin". The Catholic Encyclopedia. Vol 11. New York: Robert Appleton Company, 1911. 28 Mar. 2013
^ Lilie, Ralph-Johannes; Ludwig, Claudia; Pratsch, Thomas; Zielke, Beate (2001). "Ualentinos (#8545)". Prosopographie der mittelbyzantinischen Zeit: 1. Abteilung (641–867), Band 5 : Theophylaktos (# 8346) – az-Zubair (# 8675), Anonymi (# 10001–12149) (in German). Berlin and Boston: De Gruyter. p. 71. ISBN 978-3-11-016675-0.
^ Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1996). Handbook of British Chronology (Third revised ed.). Cambridge University Press. p. 221. ISBN 0-521-56350-X.