A common year starting on Sunday is any non-leap year (i.e. a year with 365 days) that begins on Sunday, 1 January, and ends on Sunday, 31 December. Its dominical letter hence is A. The most recent year of such kind was 2023, and the next one will be 2034 in the Gregorian calendar,[1] or, likewise, 2018 and 2029 in the obsolete Julian calendar, see below for more.
Any common year that starts on a Sunday has two Friday the 13ths: those two in this common year occur in January and October.