| 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 |
| Bahá'í calendar | -1863 – -1862 |
| Bengali calendar | -612 |
| Berber calendar | 931 |
| 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 | |
| - Bikram Samwat | 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 |
| Thai solar calendar | 524 |
Year 20 BC was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar.