| Millennium: | 2nd Millennium BC |
|---|---|
| Centuries: | 18th cent. BC – 17th cent. BC – 16th cent. BC |
| Decades: | 1650s BC 1640s BC 1630s BC – 1620s BC – 1610s BC 1600s BC 1590s BC |
| Years: | 1624 BC 1623 BC 1622 BC – 1621 BC – 1620 BC 1619 BC 1618 BC |
| Gregorian calendar | 1621 MDCXXI |
| Ab urbe condita | 2374 |
| Armenian calendar | 1070 ԹՎ ՌՀ |
| Assyrian calendar | 6371 |
| Bengali calendar | 1028 |
| Berber calendar | 2571 |
| English Regnal year | 18 Ja. 1 – 19 Ja. 1 |
| Buddhist calendar | 2165 |
| Burmese calendar | 983 |
| Byzantine calendar | 7129–7130 |
| Chinese calendar | 庚申年 (Metal Monkey) 4317 or 4257 — to — 辛酉年 (Metal Rooster) 4318 or 4258 |
| Coptic calendar | 1337–1338 |
| Discordian calendar | 2787 |
| Ethiopian calendar | 1613–1614 |
| Hebrew calendar | 5381–5382 |
| Hindu calendars | |
| - Vikram Samvat | 1677–1678 |
| - Shaka Samvat | 1542–1543 |
| - Kali Yuga | 4721–4722 |
| Holocene calendar | 11621 |
| Igbo calendar | 621–622 |
| Iranian calendar | 999–1000 |
| Islamic calendar | 1030–1031 |
| Japanese calendar | Genna 7 (元和７年) |
| Javanese calendar | 1542–1543 |
| Julian calendar | Gregorian minus 10 days |
| Korean calendar | 3954 |
| Minguo calendar | 291 before ROC 民前291年 |
| Nanakshahi calendar | 153 |
| Thai solar calendar | 2163–2164 |
The year 1621 BC