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This is the calendar for any Old Style leap year starting on Saturday, 25 March. The Old Style calendar ended the following March, on 24 March. Examples: Julian year 1564, 1620 or 1704 (see bottom tables).
A leap year is a year with 366 days, as compared to a common year, which has 365.
"Calendar in year 1802 (Russia)" (Julian calendar, starting Tuesday), webpage: Julian-1802 (Romania used Julian in 1919, when Russia adopted Gregorian).
"Calendar in year 1536 (United Kingdom)" (Julian leap starting Tuesday),
webpage: Julian-1536.