Year 621 (DCXXI) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. The denomination 621 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.
| Millennium: | 1st millennium |
|---|---|
| Centuries: |
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| Decades: |
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| Years: |
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| Gregorian calendar | 621 DCXXI |
| Ab urbe condita | 1374 |
| Armenian calendar | 70 ԹՎ Հ |
| Assyrian calendar | 5371 |
| Balinese saka calendar | 542–543 |
| Bengali calendar | 28 |
| Berber calendar | 1571 |
| Buddhist calendar | 1165 |
| Burmese calendar | −17 |
| Byzantine calendar | 6129–6130 |
| Chinese calendar | 庚辰年 (Metal Dragon) 3318 or 3111 — to — 辛巳年 (Metal Snake) 3319 or 3112 |
| Coptic calendar | 337–338 |
| Discordian calendar | 1787 |
| Ethiopian calendar | 613–614 |
| Hebrew calendar | 4381–4382 |
| Hindu calendars | |
| - Vikram Samvat | 677–678 |
| - Shaka Samvat | 542–543 |
| - Kali Yuga | 3721–3722 |
| Holocene calendar | 10621 |
| Iranian calendar | 1 BP – 0 BP |
| Islamic calendar | 1 BH – 0 BH |
| Japanese calendar | N/A |
| Javanese calendar | 511–512 |
| Julian calendar | 621 DCXXI |
| Korean calendar | 2954 |
| Minguo calendar | 1291 before ROC 民前1291年 |
| Nanakshahi calendar | −847 |
| Seleucid era | 932/933 AG |
| Thai solar calendar | 1163–1164 |
| Tibetan calendar | 阳金龙年 (male Iron-Dragon) 747 or 366 or −406 — to — 阴金蛇年 (female Iron-Snake) 748 or 367 or −405 |
