| Millennium: | 1st Millennium |
|---|---|
| Centuries: | 5th cent. – 6th cent. – 7th cent. |
| Decades: | 490s 500s 510s – 520s – 530s 540s 550s |
| Years: | 518 519 520 – 521 – 522 523 524 |
| Gregorian calendar | 521 DXXI |
| Ab urbe condita | 1274 |
| Assyrian calendar | 5271 |
| Bengali calendar | −72 |
| Berber calendar | 1471 |
| Buddhist calendar | 1065 |
| Burmese calendar | −117 |
| Byzantine calendar | 6029–6030 |
| Chinese calendar | 庚子年 (Metal Rat) 3217 or 3157 — to — 辛丑年 (Metal Ox) 3218 or 3158 |
| Coptic calendar | 237–238 |
| Discordian calendar | 1687 |
| Ethiopian calendar | 513–514 |
| Hebrew calendar | 4281–4282 |
| Hindu calendars | |
| - Vikram Samvat | 577–578 |
| - Shaka Samvat | 442–443 |
| - Kali Yuga | 3621–3622 |
| Holocene calendar | 10521 |
| Iranian calendar | 101 BP – 100 BP |
| Islamic calendar | 104 BH – 103 BH |
| Javanese calendar | 408–409 |
| Julian calendar | 521 DXXI |
| Korean calendar | 2854 |
| Minguo calendar | 1391 before ROC 民前1391年 |
| Nanakshahi calendar | −947 |
| Seleucid era | 832/833 AG |
| Thai solar calendar | 1063–1064 |
The year 521 BC