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AD 31 (XXXI) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Tiberius and Sejanus (or, less frequently, year 784 Ab urbe condita). The denomination AD 31 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.
|Gregorian calendar||AD 31|
|Ab urbe condita||784|
|Balinese saka calendar||N/A|
|Chinese calendar||庚寅年 (Metal Tiger)|
2727 or 2667
— to —
辛卯年 (Metal Rabbit)
2728 or 2668
|Coptic calendar||−253 – −252|
|- Vikram Samvat||87–88|
|- Shaka Samvat||N/A|
|- Kali Yuga||3131–3132|
|Iranian calendar||591 BP – 590 BP|
|Islamic calendar||609 BH – 608 BH|
|Julian calendar||AD 31|
|Minguo calendar||1881 before ROC|
|Seleucid era||342/343 AG|
|Thai solar calendar||573–574|
157 or −224 or −996
— to —
158 or −223 or −995
- April 6 (Good Friday) – Jesus is crucified (according to one dating scheme). He is later reported alive by His disciples.
- Lucius Aelius Sejanus is named co-Consul to Emperor Tiberius. However, Tiberius becomes aware of Sejanus' treachery and has him arrested and executed.
- Naevius Sutorius Macro becomes the leader of the Praetorian Guard after Sejanus is executed.
- April 6 – Jesus of Nazareth, (possible date of the crucifixion) (born circa 4 BC) The other possible dates also supported by scholarly consensus among a survey of 100 published scholarly biblical statements are April 7, AD 30 and April 3, AD 33.
- October 18 – Lucius Aelius Sejanus, Roman prefect and advisor (b. 20 BC)
- Claudia Livia Julia, niece and daughter-in-law of Tiberius (b. 13 BC)
- Marcus Velleius Paterculus, Roman historian and writer (b. c. 19 BC)
- Nero Julius Caesar Germanicus, grandson and heir of Tiberius (b. AD 6)
- Colin J. Humphreys and W. G. Waddington, "Dating the Crucifixion ," Nature 306 (December 22/29, 1983), pp. 743-46. 
- Colin Humphreys, The Mystery of the Last Supper Cambridge University Press 2011 ISBN 978-0-521-73200-0, page 194
- Blinzler, J. Der Prozess Jesu, fourth edition, Regensburg, Pustet, 1969, pp101-126
- Colin Humphreys, The Mystery of the Last Supper Cambridge University Press 2011 ISBN 978-0-521-73200-0, pages 14 and 62
- Vagi, David (2016). Coinage and History of the Roman Empire. Routledge. p. 107. ISBN 978-1-135-97125-0.