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 current year, **2017**, is a common year starting on Sunday in the Gregorian calendar and the next such year will be 2023, or, likewise, 2007 and 2018 in the obsolete Julian calendar, see below for more.

## Contents

## Gregorian Calendar

In the (currently used) Gregorian calendar, the 15 types of years repeat in a 400-year cycle (20871 weeks). 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 15 types of years repeat in a 28-year cycle (1461 weeks). 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 6th, 17th and 23rd year 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.