Back Ҳ. ҟ. 31 Abkhazian 31 v.C. Afrikaans 31 aC AN 31 ق م Arabic 31 قبل لميلاد ARY 31 ق م ARZ 31 e.C. AST E.ə. 31 Azerbaijani 31 да н.э. Byelorussian 31 да н. э. BE-X-OLD
| Gregorian calendar | 31 BC XXX 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) 2666 or 2606 — to — 庚寅年 (Metal Tiger) 2667 or 2607 |
| 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 XXX 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 |
Year 31 BC was either a common year starting on Tuesday, Wednesday or Thursday or a leap year starting on Tuesday or Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Antonius and Octavianus.