This is the calendar for any Old Style leap year starting on Sunday, 25 March. The Old Style calendar ended the following March, on 24 March. Examples: Julian year 1548, 1632 or 1716 (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 1548 (United Kingdom)" (Julian leap year starting
on Sunday), TimeandDate.com, 2013, webpage:
Julian-1548.