A "leap year starting on Sunday" is a year with February 29 (a leap day) in which January 1 falls on a Sunday. This simple alignment fixes the weekday of every date that year and produces a distinctive calendar layout: certain months begin on the same weekday and several holidays and observances fall on predictable weekdays. The pattern also creates the uncommon feature of three occurrences of Friday the 13th.

Calendar characteristics

Because the year begins on a Sunday, the weekday progression through months is determined by their lengths. In a leap year that starts on Sunday, January 1 is Sunday and February 29 lands on a Wednesday. March 1 therefore begins on a Thursday, and subsequent month-start weekdays follow from that point. A direct consequence is that January, April and July each begin on Sunday; any month that begins on Sunday will have its 13th day on a Friday, so this type of leap year is the only leap-year layout that produces three Friday the 13ths (in January, April and July).

Occurrence and examples

The pattern appears periodically in modern civil calendars governed by the Gregorian rules (every year divisible by 4 is normally a leap year, except century years not divisible by 400 are common). Examples of leap years that started on Sunday include 1928, 1956, 1984, 2012 and 2040. For background on the concept of a leap year and the weekday Sunday, see general calendar references. The calendar layout that yields three Friday the 13ths is shared only with a different yearly type: a common (non-leap) year that begins on Thursday; that relation is often noted when comparing year-to-year weekday shifts (common year starting on Thursday).

Holidays and notable dates

  • Martin Luther King Jr. Day (third Monday in January): January 16 in such a year.
  • Valentine's Day: Tuesday.
  • Presidents Day (third Monday in February): February 20.
  • Leap day: February 29 falls on a Wednesday.
  • St. Patrick's Day: Saturday.
  • Mother's Day (second Sunday in May): May 13.
  • Memorial Day (last Monday in May): May 28.
  • Father's Day (third Sunday in June): June 17.
  • Independence Day: Wednesday.
  • Labor Day (first Monday in September): September 3.
  • Columbus Day (second Monday in October): October 8 (the earliest possible date for that observance in the U.S.).
  • Halloween: Wednesday. Veterans Day: Sunday. Thanksgiving (fourth Thursday in November): November 22 (an earliest possible date for Thanksgiving).
  • Christmas Day: Tuesday.

Because the weekday pattern of a year is fixed by the starting weekday and whether the year is leap or common, planners and calendaring software often refer to year types rather than individual years. The Gregorian calendar repeats its full sequence of weekdays every 400 years, so layouts recur in a long cycle; however, shorter patterns arise when working with leap-year spacing (every four years, except exceptions). The presence of three Friday the 13ths in January, April and July is of interest to cultural or superstitious observers and can influence event scheduling. When comparing adjacent years, a leap year that starts on Sunday typically falls three years either side of certain common-year arrangements (for example, the common years that start on Thursday), which helps explain clustered patterns of holiday weekdays across a span of years.

Understanding this year type is useful for historical research, long-range planning, event coordination and publishing recurring schedules. For more detailed examples or printable templates, consult calendrical references and tools that enumerate year types and their weekday mappings.