Leap year starting on Monday

A leap year starting on Monday is any year with 366 days (i.e. it includes 29 February) that begins on Monday, 1 January, and ends on Tuesday, 31 December. Its dominical letters hence are GF. The most recent year of such kind was 2024, and the next one will be 2052 in the Gregorian calendar^[1] or, likewise, 2008 and 2036 in the obsolete Julian calendar.

Any leap year that starts on Monday has two Friday the 13ths: those two in this leap year occur in September and December. Common years starting on Tuesday share this characteristic.

Calendars

Calendar for any leap year starting on Monday, presented as common in many English-speaking areas
January Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31	February Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29	March Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31	April Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
May Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31	June Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30	July Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31	August Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
September Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30	October Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31	November Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30	December Su Mo Tu We Th Fr Sa 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

ISO 8601-conformant calendar with week numbers for any leap year starting on Monday (dominical letter GF)
January Wk Mo Tu We Th Fr Sa Su 01 01 02 03 04 05 06 07 02 08 09 10 11 12 13 14 03 15 16 17 18 19 20 21 04 22 23 24 25 26 27 28 05 29 30 31	February Wk Mo Tu We Th Fr Sa Su 05 01 02 03 04 06 05 06 07 08 09 10 11 07 12 13 14 15 16 17 18 08 19 20 21 22 23 24 25 09 26 27 28 29	March Wk Mo Tu We Th Fr Sa Su 09 01 02 03 10 04 05 06 07 08 09 10 11 11 12 13 14 15 16 17 12 18 19 20 21 22 23 24 13 25 26 27 28 29 30 31	April Wk Mo Tu We Th Fr Sa Su 14 01 02 03 04 05 06 07 15 08 09 10 11 12 13 14 16 15 16 17 18 19 20 21 17 22 23 24 25 26 27 28 18 29 30
May Wk Mo Tu We Th Fr Sa Su 18 01 02 03 04 05 19 06 07 08 09 10 11 12 20 13 14 15 16 17 18 19 21 20 21 22 23 24 25 26 22 27 28 29 30 31	June Wk Mo Tu We Th Fr Sa Su 22 01 02 23 03 04 05 06 07 08 09 24 10 11 12 13 14 15 16 25 17 18 19 20 21 22 23 26 24 25 26 27 28 29 30	July Wk Mo Tu We Th Fr Sa Su 27 01 02 03 04 05 06 07 28 08 09 10 11 12 13 14 29 15 16 17 18 19 20 21 30 22 23 24 25 26 27 28 31 29 30 31	August Wk Mo Tu We Th Fr Sa Su 31 01 02 03 04 32 05 06 07 08 09 10 11 33 12 13 14 15 16 17 18 34 19 20 21 22 23 24 25 35 26 27 28 29 30 31
September Wk Mo Tu We Th Fr Sa Su 35 01 36 02 03 04 05 06 07 08 37 09 10 11 12 13 14 15 38 16 17 18 19 20 21 22 39 23 24 25 26 27 28 29 40 30	October Wk Mo Tu We Th Fr Sa Su 40 01 02 03 04 05 06 41 07 08 09 10 11 12 13 42 14 15 16 17 18 19 20 43 21 22 23 24 25 26 27 44 28 29 30 31	November Wk Mo Tu We Th Fr Sa Su 44 01 02 03 45 04 05 06 07 08 09 10 46 11 12 13 14 15 16 17 47 18 19 20 21 22 23 24 48 25 26 27 28 29 30	December Wk Mo Tu We Th Fr Sa Su 48 01 49 02 03 04 05 06 07 08 50 09 10 11 12 13 14 15 51 16 17 18 19 20 21 22 52 23 24 25 26 27 28 29 01 30 31

Applicable years

Gregorian Calendar

Leap years that begin on Monday, along with those starting on Saturday and Thursday, occur least frequently: 13 out of 97 (≈ 13.4%) total leap years in a 400-year cycle of the Gregorian calendar. Their overall frequency is thus 3.25% (13 out of 400) of years.

Gregorian leap years starting on Monday^[1]

Decade	1st	2nd	3rd	4th	5th	6th	7th	8th	9th	10th
16th century	prior to first adoption (proleptic)									1596
17th century			1624			1652		1680
18th century		1720			1748			1776
19th century		1816			1844			1872
20th century		1912		1940			1968			1996
21st century			2024			2052		2080
22nd century		2120			2148			2176
23rd century		2216			2244			2272
24th century		2312		2340			2368			2396
25th century			2424			2452		2480
26th century		2520			2548			2576
27th century		2616			2644			2672

400-year cycle

0–99	24	52	80
100–199	120	148	176
200–299	216	244	272
300–399	312	340	368	396

Julian Calendar

Like all leap year types, the one starting with 1 January on a Monday 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 that means it will also repeat after 700 years, i.e. 25 cycles. The year's position in the cycle is given by the formula ((year + 8) mod 28) + 1).

Julian leap years starting on Monday

Decade	1st	2nd	3rd	4th	5th	6th	7th	8th	9th	10th
14th century	1308			1336			1364			1392
15th century		1420			1448			1476
16th century	1504			1532		1560			1588
17th century		1616			1644			1672		1700
18th century			1728			1756			1784
19th century		1812		1840			1868			1896
20th century			1924			1952		1980
21st century	2008			2036			2064			2092
22nd century		2120			2148			2176

Holidays

International

• Valentine's Day falls on a Wednesday
• The leap day (February 29) falls on a Thursday
• World Day for Grandparents and the Elderly falls on its latest possible date, July 28
• Halloween falls on a Thursday
• Christmas Day falls on a Wednesday

Roman Catholic Solemnities

• Epiphany falls on a Saturday or, in places when it is transferred to a Sunday, January 7
• Candlemas falls on a Friday
• Saint Joseph's Day falls on a Tuesday
• The Annunciation of Jesus falls on a Monday
• The Nativity of John the Baptist falls on a Monday
• The Solemnity of Saints Peter and Paul falls on a Saturday
• The Transfiguration of Jesus falls on a Tuesday
• The Assumption of Mary falls on a Thursday
• The Exaltation of the Holy Cross falls on a Saturday
• All Saints' Day falls on a Friday
• All Souls' Day falls on a Saturday
• The Feast of Christ the King falls on November 24 (or on October 27 in versions of the calendar between 1925 and 1962)
• The First Sunday of Advent falls on December 1
• The Immaculate Conception falls on a Sunday, thus transferred to Monday, December 9.
• Gaudete Sunday falls on December 15
• Rorate Sunday falls on December 22

Australia and New Zealand

• Australia Day falls on a Friday
• Waitangi Day falls on a Tuesday
• Daylight saving ends on its latest possible date, April 7 – the period of daylight saving which ends on April 7 of a leap year starting on Monday is the only period ending in any year to last 27 weeks in Australia and 28 weeks in New Zealand; in all other instances, the period of daylight saving lasts only 26 weeks in Australia and 27 weeks in New Zealand
• ANZAC Day falls on a Thursday
• Mother's Day falls on May 12
• Father's Day falls on its earliest possible date, September 1
• Daylight saving begins on September 29 in New Zealand and October 6 in Australia

British Isles

• Saint David's Day falls on a Friday
• Mother's Day falls on March 3, March 10, March 17, March 24 or March 31
• Saint Patrick's Day falls on a Sunday
• Daylight saving begins on its latest possible date, March 31
• Saint George's Day falls on a Tuesday
• Father's Day falls on June 16
• Orangeman's Day falls on a Friday
• Daylight saving ends on October 27
• Guy Fawkes Night falls on a Tuesday
• Saint Andrew's Day falls on a Saturday

Canada

• Daylight saving begins on March 10
• Mother's Day falls on May 12
• Victoria Day falls on May 20
• Father's Day falls on June 16
• Canada Day falls on a Monday
• Labour Day falls on September 2
• Thanksgiving Day falls on its latest possible date, October 14
• Daylight saving ends on November 3

United States

• Martin Luther King Jr. Day falls on its earliest possible date, January 15
• President's Day falls on February 19
• Daylight saving begins on March 10
• Mother's Day falls on May 12
• Memorial Day falls on May 27
• Father's Day falls on June 16
• Juneteenth falls on a Wednesday
• Independence Day falls on a Thursday
• Labor Day falls on September 2
• Grandparents' Day falls on September 8
• Columbus Day falls on its latest possible date, October 14 (this is the only year when Martin Luther King Jr. Day and Columbus Day are 39 weeks apart) They are 38 weeks apart in all other years
• Daylight saving ends on November 3
• Election Day falls on November 5
• Thanksgiving Day falls on its latest possible date, November 28 (this is also the only year when Martin Luther King Jr. Day and Thanksgiving are 318 days apart) They are 311 days apart in all other years