Back 1821 Abkhazian 1821 Afrikaans 1821 ALS 1821 እ.ኤ.አ. Amharic 1821 AN 1821 Arabic 1821 ARY 1821 ARZ 1821 AST 1821 AVK
| Millennium: | 2nd millennium |
|---|---|
| Centuries: | 18th century – 19th century – 20th century |
| Decades: | 1790s 1800s 1810s – 1820s – 1830s 1840s 1850s |
| Years: | 1818 1819 1820 – 1821 – 1822 1823 1824 |
| Gregorian calendar | 1821 MDCCCXXI |
| Ab urbe condita | 2574 |
| Armenian calendar | 1270 ԹՎ ՌՄՀ |
| Assyrian calendar | 6571 |
| Balinese saka calendar | 1742–1743 |
| Bengali calendar | 1228 |
| Berber calendar | 2771 |
| British Regnal year | 1 Geo. 4 – 2 Geo. 4 |
| Buddhist calendar | 2365 |
| Burmese calendar | 1183 |
| Byzantine calendar | 7329–7330 |
| Chinese calendar | 庚辰年 (Metal Dragon) 4517 or 4457 — to — 辛巳年 (Metal Snake) 4518 or 4458 |
| Coptic calendar | 1537–1538 |
| Discordian calendar | 2987 |
| Ethiopian calendar | 1813–1814 |
| Hebrew calendar | 5581–5582 |
| Hindu calendars | |
| - Vikram Samvat | 1877–1878 |
| - Shaka Samvat | 1742–1743 |
| - Kali Yuga | 4921–4922 |
| Holocene calendar | 11821 |
| Igbo calendar | 821–822 |
| Iranian calendar | 1199–1200 |
| Islamic calendar | 1236–1237 |
| Japanese calendar | Bunsei 4 (文政４年) |
| Javanese calendar | 1748–1749 |
| Julian calendar | Gregorian minus 12 days |
| Korean calendar | 4154 |
| Minguo calendar | 91 before ROC 民前91年 |
| Nanakshahi calendar | 353 |
| Thai solar calendar | 2363–2364 |
| Tibetan calendar | 阳金龙年 (male Iron-Dragon) 1947 or 1566 or 794 — to — 阴金蛇年 (female Iron-Snake) 1948 or 1567 or 795 |
1821 (MDCCCXXI) was a common year starting on Monday of the Gregorian calendar and a common year starting on Saturday of the Julian calendar, the 1821st year of the Common Era (CE) and Anno Domini (AD) designations, the 821st year of the 2nd millennium, the 21st year of the 19th century, and the 2nd year of the 1820s decade. As of the start of 1821, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.