| Millennium: | 1st millennium BC |
|---|---|
| Centuries: | 2nd century BC – 1st century BC – 1st century |
| Decades: | 50s BC 40s BC 30s BC – 20s BC – 10s BC 0s BC 0s |
| Years: | 23 BC 22 BC 21 BC – 20 BC – 19 BC 18 BC 17 BC |
| 20 BC by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishments and disestablishments categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 20 BC |
| Ab urbe condita | 734 |
| Armenian calendar | N/A |
| Assyrian calendar | 4731 |
| Bahá'í calendar | -1863–-1862 |
| Bengali calendar | -612 |
| Berber calendar | 931 |
| English Regnal year | N/A |
| Buddhist calendar | 525 |
| Burmese calendar | -657 |
| Byzantine calendar | 5489–5490 |
| Chinese calendar | 庚子年 (2617/2677) — to —
辛丑年(2618/2678) |
| Coptic calendar | -303–-302 |
| Ethiopian calendar | -27–-26 |
| Hebrew calendar | 3741–3742 |
| Hindu calendars | |
| - Vikram Samvat | 37–38 |
| - Shaka Samvat | N/A |
| - Kali Yuga | 3082–3083 |
| Holocene calendar | 9981 |
| Iranian calendar | 641 BP – 640 BP |
| Islamic calendar | 661 BH – 660 BH |
| Japanese calendar | |
| Korean calendar | 2314 |
| Minguo calendar | 1931 before ROC 民前1931年 |
| Thai solar calendar | 524 |
Year 20 BC was either a common year starting on Wednesday or Thursday or a leap year starting on Tuesday, Wednesday or Thursday (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 Appuleius and Nerva (or, less frequently, year 734 Ab urbe condita). The denomination 20 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.