Leap year starting on Sunday

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 letters hence are AG. The most recent year of such kind was 2012 and the next one will be 2040 in the Gregorian calendar or, likewise, 1996 and 2024 in the obsolete Julian calendar.
This is the only leap year with three occurrences of Friday the 13th: those three in this leap year occur three months (13 weeks) apart: in January, April, and July. Common years starting on Thursday share this characteristic, in the months of February, March, and November.
In this type of year, all dates (except 29 February) fall on their respective weekdays 58 times in the 400 year Gregorian calendar cycle. Leap years starting on Friday share this characteristic. Additionally, these types of years are the only ones which contain 54 different calendar weeks (2 partial, 52 in full) in areas of the world where Monday is considered the first day of the week.
Calendars
Applicable years
Gregorian Calendar
Leap years that begin on Sunday, along with those starting on Friday, occur most frequently: 15 of the 97 (≈ 15.46%) total leap years in a 400-year cycle of the Gregorian calendar. Thus, their overall occurrence is 3.75% (15 out of 400).
Julian Calendar
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. As the Julian calendar repeats after 28 years, it will also repeat after 700 years, i.e., 25 cycles. The formula gives the year's position in the cycle ((year + 8) mod 28) + 1).
Holidays
International
Valentine's Day falls on a Tuesday
The leap day (February 29) falls on a Wednesday
World Day for Grandparents and the Elderly falls on its earliest possible date, July 22
Halloween falls on a Wednesday
Christmas Day falls on a Tuesday
Roman Catholic Solemnities
Epiphany falls on a Friday
Candlemas falls on a Thursday
Saint Joseph's Day falls on a Monday
The Annunciation of Jesus falls on a Sunday
The Nativity of John the Baptist falls on a Sunday
The Solemnity of Saints Peter and Paul falls on a Friday
The Transfiguration of Jesus falls on a Monday
The Assumption of Mary falls on a Wednesday
The Exaltation of the Holy Cross falls on a Friday
All Saints' Day falls on a Thursday
All Souls' Day falls on a Friday
The Feast of Christ the King falls on November 25 (or on October 28 in versions of the calendar between 1925 and 1962)
The First Sunday of Advent falls on December 2
The Immaculate Conception falls on a Saturday
Gaudete Sunday falls on December 16
Rorate Sunday falls on December 23
Australia and New Zealand
Australia Day falls on a Thursday
Waitangi Day falls on a Monday
Daylight saving ends on its earliest possible date, April 1
ANZAC Day falls on a Wednesday
Mother's Day falls on May 13
Father's Day falls on September 2
Daylight saving begins on its latest possible date, September 30 in New Zealand and October 7 in Australia – this is the only leap year where the period of standard time over the winter months lasts 26 weeks in New Zealand and 27 weeks in Australia (in all other leap years, it lasts only 25 weeks in New Zealand and 26 weeks in Australia)
British Isles
Saint David's Day falls on a Thursday
Mother's Day falls on March 4, March 11, March 18, March 25 or April 1
Saint Patrick's Day falls on a Saturday
Daylight saving begins on its earliest possible date, March 25
Saint George's Day falls on a Monday
Father's Day falls on June 17
Orangeman's Day falls on a Thursday
Daylight saving ends on October 28
Guy Fawkes Night falls on a Monday
Saint Andrew's Day falls on a Friday
Canada
Daylight saving begins on March 11
Mother's Day falls on May 13
Victoria Day falls on May 21
Father's Day falls on June 17
Canada Day falls on a Sunday
Labour Day falls on September 3
Thanksgiving Day falls on its earliest possible date, October 8
Daylight saving ends on November 4
United States
Martin Luther King Jr. Day falls on January 16
President's Day falls on February 20
Daylight saving begins on March 11
Mother's Day falls on May 13
Memorial Day falls on May 28
Father's Day falls on June 17
Juneteenth falls on a Tuesday
Independence Day falls on a Wednesday
Labor Day falls on September 3
Grandparents' Day falls on September 9
Columbus Day falls on its earliest possible date, October 8
Daylight saving ends on November 4
Thanksgiving Day falls on its earliest possible date, November 22
References
Gregorian calendar
Julian calendar
Sunday