1803

Millennium: 2nd millennium
Centuries:
Decades:
Years:
December 20: U.S. increases in size with Louisiana purchase
1803 in various calendars
Gregorian calendar1803
MDCCCIII
French Republican calendar11–12
Ab urbe condita2556
Armenian calendar1252
ԹՎ ՌՄԾԲ
Assyrian calendar6553
Balinese saka calendar1724–1725
Bengali calendar1210
Berber calendar2753
British Regnal year43 Geo. 3 – 44 Geo. 3
Buddhist calendar2347
Burmese calendar1165
Byzantine calendar7311–7312
Chinese calendar壬戌年 (Water Dog)
4500 or 4293
    — to —
癸亥年 (Water Pig)
4501 or 4294
Coptic calendar1519–1520
Discordian calendar2969
Ethiopian calendar1795–1796
Hebrew calendar5563–5564
Hindu calendars
 - Vikram Samvat1859–1860
 - Shaka Samvat1724–1725
 - Kali Yuga4903–4904
Holocene calendar11803
Igbo calendar803–804
Iranian calendar1181–1182
Islamic calendar1217–1218
Japanese calendarKyōwa 2
(享和2年)
Javanese calendar1729–1730
Julian calendarGregorian minus 12 days
Korean calendar4136
Minguo calendar109 before ROC
民前109年
Nanakshahi calendar335
Thai solar calendar2345–2346
Tibetan calendar阳水狗年
(male Water-Dog)
1929 or 1548 or 776
    — to —
阴水猪年
(female Water-Pig)
1930 or 1549 or 777
January 5: steamboat Charlotte Dundas is demonstrated.
September 23: Battle of Assaye
Completing the Louisiana Purchase from France .

1803 (MDCCCIII) was a common year starting on Saturday of the Gregorian calendar and a common year starting on Thursday of the Julian calendar, the 1803rd year of the Common Era (CE) and Anno Domini (AD) designations, the 803rd year of the 2nd millennium, the 3rd year of the 19th century, and the 4th year of the 1800s decade. As of the start of 1803, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.