| Aug 23Wed | Ganesh ChaturthiTentativeReligion · Hinduism · to Sep 2 | – | annual | WikipediaComputed (rule) | in 2 yr |
| Aug 24Thu | Minnesota State Fair 2028Culture · Minnesota · to Sep 4 · State Fairgrounds, Falcon Heights | State Fairgrounds, Falcon Heights | annual | Minnesota State FairComputed (rule) | in 2 yr |
| Sep 1Fri | Bear season opens (MN)Outdoors · Hunting · to Oct 15 · Permit areas & no-quota area | Permit areas & no-quota area | annual | Minnesota DNR | in 2 yr |
| Sep 2Sat | Wilhelm Ostwald, born 1853 (175 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 3Sun | Full moon: Corn MoonSky · Moon phases · 6:48 pm CT | – | monthly | NASAComputed (rule) | in 2 yr |
| Ghost Festival (Zhongyuan)Religion · Buddhism | – | annual | Hong Kong ObservatoryComputed (rule) | in 2 yr |
| 150th anniversary: The passenger steamship SS Princess Alice sank in the River Thames after...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 4Mon | Labor DayHolidays · United States · United States | United States | annual | Nager.Date | in 2 yr |
| Labor Day (Canada)Holidays · Canada · Canada | Canada | annual | Nager.Date | in 2 yr |
| Sep 5Tue | International Day of CharityObservances · UN international days | – | annual | United Nations | in 2 yr |
| International Day of the World’s Indigenous Women and GirlsObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 6Wed | Mercury at greatest eastern elongationSky · Planets | – | recurring | Astronomy EngineComputed (rule) | in 2 yr |
| Sep 7Thu | 250th anniversary: Anglo-French War: Having established an alliance with the United States, France...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Independence Day (Brazil)Holidays · Brazil · Brazil | Brazil | annual | Nager.Date | in 2 yr |
| International Day of Clean Air for Blue SkiesObservances · UN international days | – | annual | United Nations | in 2 yr |
| International Day of Police CooperationObservances · UN international days | – | annual | United Nations | in 2 yr |
| World Duchenne Awareness DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 8Fri | International Literacy DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 9Sat | Leo Tolstoy, born 1828 (200 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| International Day to Protect Education from AttackObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 10Sun | National Grandparents DayObservances · Days | – | annual | US CodeComputed (rule) | in 2 yr |
| Sep 11Mon | 50th anniversary: British medical photographer Janet Parker became the last recorded person to...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Last quarter moonSky · Moon phases · 7:46 pm CT | – | monthly | NASAComputed (rule) | in 2 yr |
| Theodor W. Adorno, born 1903 (125 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 12Tue | 100th anniversary: The Okeechobee hurricane first struck the island of GuadeloupeHistory · Anniversaries | – | annual | Wikipedia | in 2 yr |
| 25th anniversary: The first public release of Steam, a distribution service for computer games,...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| 25th anniversary: Typhoon Maemi, the strongest recorded typhoon to strike South Korea, made...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| United Nations Day for South-South CooperationObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 13Wed | Claudette Colbert, born 1903 (125 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 14Thu | 25th anniversary: President Kumba Ialá (pictured) of Guinea-Bissau was deposed in a bloodless...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 15Fri | National Hispanic Heritage MonthObservances · Heritage months · to Oct 15 | – | annual | Library of Congress and partnersComputed (rule) | in 2 yr |
| International Day of DemocracyObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 16Sat | Independence Day (Mexico)Holidays · Mexico · Mexico | Mexico | annual | Nager.Date | in 2 yr |
| International Day for Interventional CardiologyObservances · UN international days | – | annual | United Nations | in 2 yr |
| International Day for the Preservation of the Ozone LayerObservances · UN international days | – | annual | United Nations | in 2 yr |
| International Day of Science, Technology and Innovation for the SouthObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 17Sun | 150th anniversary: A British surveyor was detained by the Zulu on the border with the Colony of NatalHistory · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Anastacia, born 1968 (60 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| World Patient Safety DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 18Mon | New moonSky · Moon phases · 1:24 pm CT | – | monthly | NASAComputed (rule) | in 2 yr |
| Respect for the Aged Day (Japan)Holidays · Japan · Japan | Japan | annual | Nager.Date | in 2 yr |
| 50s, born 53 (1975 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| International Equal Pay DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 19Tue | Sharad NavaratriTentativeReligion · Hinduism · to Sep 27 | – | annual | WikipediaComputed (rule) | in 2 yr |
| Jeremy Irons, born 1948 (80 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 20Wed | George R. R. Martin, born 1948 (80 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| World Cleanup DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 21Thu | Rosh HashanahReligion · Judaism · to Sep 22 | – | annual | HebcalComputed (rule) | in 2 yr |
| International Day of PeaceObservances · UN international days | – | annual | United Nations | in 2 yr |
| Heike Kamerlingh Onnes, born 1853 (175 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 22Fri | September equinoxSky · Solstices and equinoxes · 6:45 am CT | – | annual | US Naval ObservatoryComputed (rule) | in 2 yr |
| MabonReligion · Pagan and Wiccan | – | annual | Wheel of the YearComputed (rule) | in 2 yr |
| Autumnal Equinox Day (Japan)Holidays · Japan · Japan | Japan | annual | Nager.Date | in 2 yr |
| 25th anniversary: Dolphin, the first emulator for the GameCube that could run commercial video...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Andrea Bocelli, born 1958 (70 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 23Sat | National Hunting and Fishing DayOutdoors · Parks and public lands | – | annual | National Hunting and Fishing DayComputed (rule) | in 2 yr |
| National Public Lands DayOutdoors · Parks and public lands | – | annual | National Park ServiceComputed (rule) | in 2 yr |
| 225th anniversary: Maratha troops were defeated by forces of the British East India Company at the...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| International Day of Sign LanguagesObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 24Sun | Fast of GedaliahReligion · Judaism | – | annual | HebcalComputed (rule) | in 2 yr |
| 125th anniversary: Alfred Deakin became the second Australian prime minister, succeeding Edmund BartonHistory · Anniversaries | – | annual | Wikipedia | in 2 yr |
| World Maritime DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 25Mon | 50th anniversary: While on approach to San Diego International Airport, Pacific Southwest...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Heritage Day (South Africa)Holidays · South Africa · South Africa | South Africa | annual | Nager.Date | in 2 yr |
| First quarter moonSky · Moon phases · 8:10 am CT | – | monthly | NASAComputed (rule) | in 2 yr |
| Will Smith, born 1968 (60 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| Sep 26Tue | 100th anniversary: The Republic of China adopted Gwoyeu Romatzyh (designer pictured) as the...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| International Day for the Total Elimination of Nuclear WeaponsObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 27Wed | Dussehra (Vijayadashami)TentativeReligion · Hinduism | – | annual | WikipediaComputed (rule) | in 2 yr |
| World Tourism DayObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 28Thu | 100th anniversary: Scottish biologist and pharmacologist Alexander Fleming (pictured) discovered...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| 50th anniversary: Pope John Paul I died only 33 days after his papal election due to an apparent...History · Anniversaries | – | annual | Wikipedia | in 2 yr |
| Naomi Watts, born 1968 (60 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| International Day for Universal Access to InformationObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 29Fri | Neptune at oppositionSky · Planets | – | about yearly | Astronomy EngineComputed (rule) | in 2 yr |
| International Day of Awareness of Food Loss and WasteObservances · UN international days | – | annual | United Nations | in 2 yr |
| Sep 30Sat | Yom KippurReligion · Judaism | – | annual | HebcalComputed (rule) | in 2 yr |
| National Day for Truth and Reconciliation (Canada)Holidays · Canada · Canada | Canada | annual | Nager.Date | in 2 yr |
| Elie Wiesel, born 1928 (100 years)People · Birth anniversaries | – | annual | Wikipedia | in 2 yr |
| International Translation DayObservances · UN international days | – | annual | United Nations | in 2 yr |
