Common year starting on Sunday

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 2006 and the next one will be 2017 in the Gregorian calendar^[1] or, likewise, 2007 and 2018 in the obsolete Julian calendar, see below for more.

Calendars

Applicable years

The 15 types of years repeat in a 28-year cycle (1461 weeks) in the Julian calendar. Each leap-year dominical letter occurs exactly once and every common letter thrice.

The final two digits of Julian years repeat after 700 years, i.e. 25 cycles. When starting to count in 2001 for instance, every 1st, 7th and 18th year (equivalent to #17, #23 and #06 in the table) of these Julian cycles is a common year that starts on a Sunday, i.e. ca. 10.71 % of all years. They are always 6 or 11 years apart.

The 15 types of years repeat in a 400-year cycle (20871 weeks) in the Gregorian calendar. 13 leap 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.

Notes

1. 1 2 Robert van Gent (2005). "The Mathematics of the ISO 8601 Calendar". Utrecht University, Department of Mathematics. 
2. ↑ Robert H. van Gent (2005). "Mathematics of the ISO calendar". Department of Mathematics at Utrecht University.