1805 (MDCCCV) was a common year starting on Tuesday of the Gregorian calendar and a common year starting on Sunday of the Julian calendar, the 1805th year of the Common Era (CE) and Anno Domini (AD) designations, the 805th year of the 2nd millennium, the 5th year of the 19th century, and the 6th year of the 1800s decade. As of the start of 1805, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.

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