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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 or, likewise, 2008 and 2036 in the obsolete Julian calendar.

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

Additionally, this type of year has three months (January, April, and July) beginning exactly on the first day of the week, in areas which Monday is considered the first day of the week, Common years starting on Friday share this characteristic on the months of February, March, and November.

Calendars

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.

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).

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

References

1. ^ Robert van Gent (2017). "The Mathematics of the ISO 8601 Calendar". Utrecht University, Department of Mathematics. Retrieved 20 July 2017.

• Gregorian calendar
• Monday