Leap year starting on Sunday

A leap year starting on Sunday is any year with 366 days (i.e. it includes 29 February) that begins on Sunday, 1 January, and ends on Monday, 31 December. Its dominical letter hence is AG, such as the years 1956, 1984, 2012, 2040, 2068, 2096, and 2108 in the Gregorian calendar or, likewise, 1996 and 2024 in the obsolete Julian calendar.

This leap year has the most occurrences of Friday the 13th (common years starting on Thursday share this feature). Each instance of Friday the 13th is three months apart in January, April, and July. Uniquely, these instances are also 13 weeks apart from one another.

Calendar for any leap year starting on Sunday,
presented as common in many English-speaking areas

ISO 8601-conformant calendar with week numbers for
any leap year starting on Sunday (dominical letter AG)

Leap years beginning on Sunday, along with those that start on Friday, occur most frequently. In a cycle of 400 years, exactly 97 are leap years and those that begin on Sunday occur 15 times; thus the overall occurrence of such year is 3.75% (15 out of 400 total years) or approximately 15.5% (15 out of 97) if just leap years are taken into consideration.

Like all leap year types, the one starting with 1 January on a Sunday occurs exactly once in a 28-year cycle in the Julian calendar, i.e. in 3.57% of years.

The final two digits of Julian years repeat after 700 years, i.e. 25 cycles.

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