| Millennium: | 2nd millennium |
|---|---|
| Centuries: | |
| Decades: | |
| Years: |
| 1721 by topic |
|---|
| Arts and science |
| Countries |
| Lists of leaders |
| Birth and death categories |
| Establishments and disestablishments categories |
| Works category |
| Gregorian calendar | 1721 MDCCXXI |
| Ab urbe condita | 2474 |
| Armenian calendar | 1170 ԹՎ ՌՃՀ |
| Assyrian calendar | 6471 |
| Balinese saka calendar | 1642–1643 |
| Bengali calendar | 1128 |
| Berber calendar | 2671 |
| British Regnal year | 7 Geo. 1 – 8 Geo. 1 |
| Buddhist calendar | 2265 |
| Burmese calendar | 1083 |
| Byzantine calendar | 7229–7230 |
| Chinese calendar | 庚子年 (Metal Rat) 4418 or 4211 — to — 辛丑年 (Metal Ox) 4419 or 4212 |
| Coptic calendar | 1437–1438 |
| Discordian calendar | 2887 |
| Ethiopian calendar | 1713–1714 |
| Hebrew calendar | 5481–5482 |
| Hindu calendars | |
| - Vikram Samvat | 1777–1778 |
| - Shaka Samvat | 1642–1643 |
| - Kali Yuga | 4821–4822 |
| Holocene calendar | 11721 |
| Igbo calendar | 721–722 |
| Iranian calendar | 1099–1100 |
| Islamic calendar | 1133–1134 |
| Japanese calendar | Kyōhō 6 (享保６年) |
| Javanese calendar | 1645–1646 |
| Julian calendar | Gregorian minus 11 days |
| Korean calendar | 4054 |
| Minguo calendar | 191 before ROC 民前191年 |
| Nanakshahi calendar | 253 |
| Thai solar calendar | 2263–2264 |
| Tibetan calendar | 阳金鼠年 (male Iron-Rat) 1847 or 1466 or 694 — to — 阴金牛年 (female Iron-Ox) 1848 or 1467 or 695 |
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1721 (MDCCXXI) was a common year starting on Wednesday of the Gregorian calendar and a common year starting on Sunday of the Julian calendar, the 1721st year of the Common Era (CE) and Anno Domini (AD) designations, the 721st year of the 2nd millennium, the 21st year of the 18th century, and the 2nd year of the 1720s decade. As of the start of 1721, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.