Overview

A "common year starting on Sunday" is a 365-day calendar year in which January 1 is a Sunday. In the dominical-letter system this year carries the letter A; in the Doomsday algorithm the year's anchor day falls on Tuesday. The pattern repeats in predictable cycles in both the Gregorian and Julian calendars and determines weekday assignments for every date that year.

Key characteristics

Because the year is not a leap year it has 365 days and advances the weekday of any date by one day from the previous year. A common year that begins on Sunday has a distinctive layout: months' weekdays follow a sequence that places certain holidays on consistent weekdays. For example, in this type of year:

  • Martin Luther King Jr. Day (third Monday in January) falls on January 16.
  • Valentine's Day (February 14) falls on a Tuesday.
  • Mother's Day (second Sunday in May) falls on its latest possible date, May 14.
  • Memorial Day (last Monday in May) is May 29, and Veterans Day (November 11) is on a Saturday.

Holidays and notable dates

Other commonly observed dates line up as follows: Presidents Day on February 20, St. Patrick's Day on a Friday, Father's Day on June 18, Independence Day on a Tuesday, Labor Day on September 4, Columbus Day on October 9, Halloween on a Tuesday, Thanksgiving on November 23, and Christmas on a Monday. This alignment is useful for planners and historians when reconstructing weekdays for past events or scheduling recurring annual activities.

Friday the 13th and calendar trivia

One notable feature of this pattern is that it produces two occurrences of Friday the 13th during the year: in January and October. Among common years, only those that start on Sunday, Monday, or Tuesday have two Friday the 13ths. Understanding these distributions helps with cultural references and risk-avoidance planning that rely on that superstition.

Examples and calendar systems

Specific recent examples of Gregorian calendar years with this pattern include 1978, 1989, 1995, 2006, 2017, and 2023. In the Julian calendar an equivalent alignment occurred in years such as 2018 and 2029. When checking a historical date it is important to note which calendar (Gregorian or Julian) was in use at the time.

Further reading and tools

To explore more about calendar calculations and related topics, consult general calendar references and algorithm descriptions such as the Doomsday rule and dominical letters. Useful starting points and tools include a modern calendar overview, the concept of a common year, and the weekday name Sunday. For historical examples see entries for years 1978, 1989, 1995, 2006, 2017, and 2023 (Gregorian), and comparable Julian years such as 2018 and 2029.

For comparisons with other starting weekdays see pages on common year starting on Monday and common year starting on Tuesday. For the distinction between leap years and common years consult a primer on the leap year rule.