Common year starting on Sunday


A common year starting on Sunday is any non-leap year 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 2017 and the next one will be 2023 in the Gregorian calendar, or, likewise, 2018 and 2029 in the obsolete Julian calendar, see [|below for more]. Any common year that starts on Sunday, Monday or Tuesday has two Friday the 13ths. This common year contains two Friday the 13ths in January and October.

Calendars

Applicable years

Gregorian Calendar

In the Gregorian calendar, alongside Monday, Wednesday, Friday or Saturday, the fourteen types of year repeat in a 400-year cycle. Forty-three common years per cycle or exactly 10.75% start on a Sunday. The 28-year sub-cycle does only span across century years divisible by 400, e.g. 1600, 2000, and 2400.

Julian Calendar

In the now-obsolete Julian calendar, the fourteen types of year repeat in a 28-year cycle. A leap year has two adjoining dominical letters. This sequence occurs exactly once within a cycle, and every common letter thrice.
As the Julian calendar repeats after 28 years that means it will also repeat after 700 years, i.e. 25 cycles. The year's position in the cycle is given by the formula + 1). Years 11, 22 and 28 of the cycle are common years beginning on Sunday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Sunday.