31 BC

31 BC in various calendars
Gregorian calendar	31 BC; XXXI BC
Ab urbe condita	723
Ancient Egypt era	XXXIII dynasty, 293
- Pharaoh	Cleopatra VII, 21
Ancient Greek era	187th Olympiad, year 2
Assyrian calendar	4720
Balinese saka calendar	N/A
Bengali calendar	−623
Berber calendar	920
Buddhist calendar	514
Burmese calendar	−668
Byzantine calendar	5478–5479
Chinese calendar	己丑年 (Earth Ox); 2667 or 2460; — to —; 庚寅年 (Metal Tiger); 2668 or 2461
Coptic calendar	−314 – −313
Discordian calendar	1136
Ethiopian calendar	−38 – −37
Hebrew calendar	3730–3731
Hindu calendars
- Vikram Samvat	26–27
- Shaka Samvat	N/A
- Kali Yuga	3070–3071
Holocene calendar	9970
Iranian calendar	652 BP – 651 BP
Islamic calendar	672 BH – 671 BH
Javanese calendar	N/A
Julian calendar	31 BC; XXXI BC
Korean calendar	2303
Minguo calendar	1942 before ROC; 民前1942年
Nanakshahi calendar	−1498
Seleucid era	281/282 AG
Thai solar calendar	512–513
Tibetan calendar	阴土牛年; (female Earth-Ox); 96 or −285 or −1057; — to —; 阳金虎年; (male Iron-Tiger); 97 or −284 or −1056

Millennium:	1st millennium BC
Centuries:	2nd century BC; 1st century BC ; 1st century;
Decades:	50s BC; 40s BC; 30s BC ; 20s BC; 10s BC;
Years:	34 BC; 33 BC; 32 BC; 31 BC ; 30 BC; 29 BC; 28 BC;

Year 31 BC was either a common year starting on Tuesday, Wednesday or Thursday or a leap year starting on Tuesday or Wednesday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a common year starting on Tuesday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Antonius and Caesar or as Caesar and Messalla (or, less frequently, year 723 Ab urbe condita). The denomination 31 BC 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	31 BC XXXI BC
Ab urbe condita	723
Ancient Egypt era	XXXIII dynasty, 293
- Pharaoh	Cleopatra VII, 21
Ancient Greek era	187th Olympiad, year 2
Assyrian calendar	4720
Balinese saka calendar	N/A
Bengali calendar	−623
Berber calendar	920
Buddhist calendar	514
Burmese calendar	−668
Byzantine calendar	5478–5479
Chinese calendar	己丑年 (Earth Ox) 2667 or 2460 — to — 庚寅年 (Metal Tiger) 2668 or 2461
Coptic calendar	−314 – −313
Discordian calendar	1136
Ethiopian calendar	−38 – −37
Hebrew calendar	3730–3731
Hindu calendars
- Vikram Samvat	26–27
- Shaka Samvat	N/A
- Kali Yuga	3070–3071
Holocene calendar	9970
Iranian calendar	652 BP – 651 BP
Islamic calendar	672 BH – 671 BH
Javanese calendar	N/A
Julian calendar	31 BC XXXI BC
Korean calendar	2303
Minguo calendar	1942 before ROC 民前1942年
Nanakshahi calendar	−1498
Seleucid era	281/282 AG
Thai solar calendar	512–513
Tibetan calendar	阴土牛年 (female Earth-Ox) 96 or −285 or −1057 — to — 阳金虎年 (male Iron-Tiger) 97 or −284 or −1056