1840

Centuries:	18th century 19th century 20th century
Decades:	1820s 1830s 1840s 1850s 1860s
Years:	1837 1838 1839 1840 1841 1842 1843
Categories:	Births - Deaths Establishments - Publications
Media:	1840 (Events)

1840 was a leap year of the Gregorian calendar and a leap year of the Julian calendar, the 1840th year of the Common Era (CE), the 40th year of the 19th century, and the 1st year of the 1840s decade. As of the start of 1840, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.