- April 1 Earliest day on which Sizdah Be-dar can fall, while April 2 is the latest; celebrated on the thirteenth day after vernal equinox. (Iran)
- April 2 Latest day on which Sizdah be dar may fall. (Iran)
- April 15 Latest day on which New Year festivals in South and Southeast Asian cultures can fall. (see April 14)
- April 19 Earliest day on which First Day of Summer or Sumardagurinn fyrsti can fall, while April 25 is the latest; celebrated on the first Thursday after April 18. (Iceland)
- August 1 Earliest date on which Caribana celebration can fall, celebrated on the first Weekend of August. (Toronto)
- August 1 Earliest date on which Emancipation Day can fall, celebrated on the first Monday of August. (Anguilla, the Bahamas, British Virgin Islands)
- August 1 Earliest date on which Commerce Day, or Frídagur verslunarmanna, can fall; celebrated on the first Monday of August. (Iceland)
- August 1 Earliest date on which International Friendship Day can fall, celebrated on the first Sunday of August.
- August 8 Earliest day on which Melon Day can fall, while August 14 is the latest; celebrated on the second Sunday in August. (Turkmenistan)
- August 15 Earliest day on which Day of Hearts can fall, while August 21 is the latest; celebrated on the third Monday in August. (area around Haarlem and Amsterdam)
- August 22 Earliest ᾓday on which National Heroes' Day can fall, while August 28 is the latest; celebrated on the fourth Monday in August. (the Philippines)
- August 24 Earliest date on which the Notting Hill Carnival can fall, while August 31 is the latest; celebrated on last Monday in August and the day before. (Notting Hill)
- August 25 Earliest date on which La Tomatina can fall, while August 31 is the latest; celebrated on the last Wednesday in August. (Buñol)
- December 20 Earliest date for Winter solstice's eve:
- December 21 Earliest date for the winter solstice:
- December 21 Earliest date for Yule in the northern hemisphere, and Midsummer in the southern hemisphere. (Neopagan Wheel of the Year)
- February 2 Earliest day on which Shrove Monday can fall, while March 8 is the latest; celebrated on Monday before Ash Wednesday. (Christianity)
- February 3 Earliest day on which Shrove Tuesday can fall, while March 9 is the latest; celebrated on Tuesday before Ash Wednesday. (Christianity)
- February 4 Earliest day on which Ash Wednesday can fall, while March 10 is the latest; celebrated on the first day of Lent. (Christianity)
- February 15 Earliest day on which Family Day can fall, while February 21 is the latest; celebrated on the third Monday in February. (Canada)
- February 15 Earliest day on which Washington's Birthday can fall, while February 21 is the latest; celebrated on the third Monday in February. (United States)
- January 1 Earliest day on which Handsel Monday can fall, while January 7 is the latest; celebrated on the first Monday of the year. (Scotland)
- January 8 Earliest day on which Children's Day can fall, while January 15 is the latest; celebrated on the second Saturday in January. (Thailand)
- January 15 Earliest day on which International Fetish Day can fall, while January 21 is the latest; celebrated on the third Friday in January.
- January 15 Earliest day on which Martin Luther King, Jr. Day can fall, while January 21 is the latest; celebrated on the third Monday in January. (United States)
- July 1 Earliest day on which St Pauls Carnival can fall, while July 7 is the latest; celebrated on the first Saturday in July. (Bristol)
- July 14 Earliest day on which the first day of Gentse Feesten can fall, while July 20 is the latest; celebrated on Saturday before July 21. (Ghent)
- July 15 Earliest day on which Marine Day can fall, while July 21 is the latest; celebrated on the third Monday of July. (Japan)
- June 15 Earliest day on which Father's Day can fall, while June 21 is the latest; celebrated on the third Sunday in June. (United States)
- June 20 Earliest date for the summer solstice:
- March 1 Earliest day on which Casimir Pulaski Day can fall, while March 7 is the latest; celebrated on the first Monday in March. (Illinois)
- March 1 Earliest day on which Laetare Sunday can fall, while April 4 is the latest; celebrated on the fourth Sunday of Lent. (Western Christianity), and its related observances:
- March 8 Earliest day on which Canberra Day can fall, while March 14 is the latest; celebrated on the second Monday in March. (Australian Capital Territory)
- March 8 Earliest day on which Commonwealth Day can fall, while March 14 is the latest; celebrated on the second Monday in March. (Commonwealth of Nations)
- March 8 Earliest day on which Passion Sunday can fall, while April 11 is the latest; observed on the fifth Sunday of Lent. (Christianity)
- March 15 Earliest day on which Palm Sunday can fall, while April 18 is the latest; celebrated on the sixth Sunday of Lent. (Christianity)
- March 18 Earliest day on which Holy Wednesday can fall, while April 21 is the latest; celebrated on the week before Easter. (Christianity)
- March 19 Earliest day on which Maundy Thursday can fall, while April 22 is the latest; celebrated on Thursday before Easter. (Christianity)
- March 20 Earliest date for the vernal equinox:
- March 20 Earliest day on which Good Friday can fall, while April 23 is the latest; celebrated on Friday before Easter. (Christianity)
- March 21 Earliest day on which Holy Saturday can fall, while April 24 is the latest; celebrated on Saturday before Easter. (Christianity)
- March 22 Earliest date on which Easter Sunday can fall, while April 25 is the latest. (Christianity)
- March 23 Earliest day on which Easter Monday can fall, while April 26 is the latest; celebrated on Monday after Easter. (Christianity):
- March 25 Earliest day on which Seward's Day can fall, while March 31 is the latest; celebrated on the last Monday in March. (Alaska)
- May 1 Earliest date on which National Day of Prayer can fall, while May 7 is the latest; celebrated on the first Thursday in May. (United States)
- May 3 Earliest date on which National Teacher's Day can fall, while May 9 is the latest; celebrated on the Tuesday of the first full week of May. (United States)
- May 6 Earliest day for Military Spouse Day, while May 12 is the latest, celebrated on the Friday before Mother's Day. (United States)
- May 8 Earliest Day for Mother's Day, while May 14 is the latest; celebrated on the second Sunday of May. (United States)
- May 8 Earliest Day for World Fair Trade Day, while May 14 is the latest; celebrated on the second Sunday of May. (International)
- May 10 Earliest possible date on which Pentecost can fall, while June 13 is the latest; celebrated seven weeks after Easter Day. (Christianity)
- May 11 Earliest date on which Whit Monday can fall, while June 14 is the latest; celebrated on the day after Pentecost. (Christianity)
- May 15 Earliest date on which Armed Forces Day can fall, while May 21 is the latest; celebrated on the third Saturday of May. (United States)
- May 15 Earliest date on which Bike-to-Work Day can fall, while May 21 is the latest; celebrated on the third Friday of May. (United States)
- May 17 Earliest date on which Trinity Sunday can fall, while June 20 is the latest; celebrated on the first Sunday after Pentecost. (Western Christianity)
- May 21 Earliest date on which Corpus Christi can fall, while June 24 is the latest; held on Thursday after Trinity Sunday. (Roman Catholic Church)
- May 29 Earliest date on which Feast of the Sacred Heart can fall, while July 2 is the latest; celebrated 19 days after Pentecost. (Roman Catholic Church)
- November 2 Earliest day on which Election Day can fall, while November 8 is the latest. (United States)
- November 8 Earliest day on which Remembrance Sunday can fall, while November 14 is the latest; celebrated on the second Sunday in November. (United Kingdom)
- November 13 Earliest day on which National Day of Mourning or Volkstrauertag can fall, observed two Sundays before the first of Advent. (Germany)
- November 15 Earliest day on which Great American Smokeout can fall, while November 21 is the latest; celebrated on the third Thursday in November (United States)
- November 17 Earliest day on which National Survivors of Suicide Day can fall, while November 23 is the latest; celebrated on Saturday before Thanksgiving. (United States)
- November 20 Earliest day on which the Feast of Christ the King can fall, while November 26 is the latest; celebrated on the last Sunday before Advent. (Roman Catholic Church)
- November 22 Earliest day on which Thanksgiving Day can fall, while November 28 is the latest; celebrated on the fourth Thursday of November. (United States)
- November 23 Earliest day on which Black Friday can fall, while November 29 is the latest; celebrated on the day after Thanksgiving. (United States)
- November 26 Earliest day on which Cyber Monday can fall, while December 2 is the latest; observed on the first Monday after Thanksgiving. (United States)
- November 27 Earliest date on which Advent Sunday can fall, while December 3 is the latest; celebrated on the Sunday nearest to St. Andrew's Day. (Western Christianity)
- October 1 Earliest day on which World Habitat Day can fall, while October 7 is the latest; celebrated on the first Monday of October. (International)
- October 8 Earliest date on which Columbus Day can fall, on the second Monday of October. (United States)
- October 8 Earliest date on which the first day of Fire Prevention Week can fall, while October 14 is the latest. (United States and Canada)
- October 15 Earliest day on which Sweetest Day can fall, while October 21 is the latest. (Great Lakes Region)
- October 22 Earliest day for Make a Difference Day, while October 28 is the latest; celebrated on the fourth Saturday in October (United States)
- September 1 Earliest date on which Labor Day can fall, while September 7 is the latest; celebrated on the first Monday in September. (United States)
- September 5 Earliest date on which Jeûne genevois can fall, while September 11 is the latest; celebrated on Thursday after the first Sunday of September. (Canton of Geneva)
- September 8 Earliest day on which Auditor's Day can fall, while September 14 is the latest; celebrated on the second Sunday in September. (Church of Scientology)
- September 11 Earliest date on which Enkutatash can fall, while September 12 is the latest, celebrated on the first day of Mäskäräm. (Ethiopia)
- September 12 Earliest date on which Programmers' Day can fall, while September 13 is the latest, celebrated on the 256th day of the year. (Russia and programmers around the world)
- September 15 Earliest day on which POW/MIA Recognition Day can fall, celebrated on the third Friday in September. (United States)
- September 15 Earliest day on which Prinsjesdag can fall, celebrated on the third Tuesday in September. (Netherlands)
- September 15 Earliest day on which German-American Steuben Parade can fall, celebrated on the third Saturday in September. (United States, especially New York City)
- September 22 Earliest date for the autumnal equinox:
|