| Millennium: | 1st millennium BC |
|---|---|
| Centuries: | |
| Decades: | |
| Years: |
| 40 BC by topic |
| Politics |
|---|
| Categories |
| Gregorian calendar | 40 BC XL BC |
| Ab urbe condita | 714 |
| Ancient Egypt era | XXXIII dynasty, 284 |
| - Pharaoh | Cleopatra VII, 12 |
| Ancient Greek era | 185th Olympiad (victor)¹ |
| Assyrian calendar | 4711 |
| Balinese saka calendar | N/A |
| Bengali calendar | −632 |
| Berber calendar | 911 |
| Buddhist calendar | 505 |
| Burmese calendar | −677 |
| Byzantine calendar | 5469–5470 |
| Chinese calendar | 庚辰年 (Metal Dragon) 2658 or 2451 — to — 辛巳年 (Metal Snake) 2659 or 2452 |
| Coptic calendar | −323 – −322 |
| Discordian calendar | 1127 |
| Ethiopian calendar | −47 – −46 |
| Hebrew calendar | 3721–3722 |
| Hindu calendars | |
| - Vikram Samvat | 17–18 |
| - Shaka Samvat | N/A |
| - Kali Yuga | 3061–3062 |
| Holocene calendar | 9961 |
| Iranian calendar | 661 BP – 660 BP |
| Islamic calendar | 681 BH – 680 BH |
| Javanese calendar | N/A |
| Julian calendar | 40 BC XL BC |
| Korean calendar | 2294 |
| Minguo calendar | 1951 before ROC 民前1951年 |
| Nanakshahi calendar | −1507 |
| Seleucid era | 272/273 AG |
| Thai solar calendar | 503–504 |
| Tibetan calendar | 阳金龙年 (male Iron-Dragon) 87 or −294 or −1066 — to — 阴金蛇年 (female Iron-Snake) 88 or −293 or −1065 |
Year 40 BC was either a common year starting on Thursday, Friday or Saturday or a leap year starting on Thursday or Friday (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 Friday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Calvinus and Pollio (or, less frequently, year 714 Ab urbe condita). The denomination 40 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.