Constitution Week, runs from September 17–23 Heroes' Day (Angola) Marathwada Liberation Day (India) National Apple Dumpling Day (United States) National Monte Cristo Sandwich Day (United States) Operation Market Garden Anniversary is still remembered with parachuting and dedications on this day. (Netherlands) Teachers' Day (Honduras) Von Steuben Day. (United States), weekend of the week of September 17. September 18 Day of National Music (Azerbaijan) First day of Fiestas Patrias (Chile) or Dieciocho (Chile) Island Language Day (Okinawa Prefecture, Japan) National Cheeseburger Day (United States) Navy Day (Croatia) World Water Monitoring Day (International) September 19 Armed Forces Day (Chile) Day of the First Public Appearance of the Slovak National Council Feast of San Gennaro Second day of Fiestas Patrias (Chile) Independence Day (Saint Kitts and Nevis) International Talk Like a Pirate Day National Butterscotch Pudding Day (United States) September 20 Independence Day of South Ossetia (not fully recognized) National Pepperoni Pizza Day (United States) National Punch Day (United States) National Rum Punch Day (United States) National Youth Day (Thailand) Oil Workers' Day (Azerbaijan) Universal Children's Day (Germany) September 21 Arbor Day (Brazil) Commemoration of the Declaration of Martial Law (Philippines) Customs Service Day (Poland) Founder's Day and National Volunteer Day (Ghana) Independence Day, celebrates the independence of Armenia from the Soviet Union in 1991. Independence Day, celebrates the independence of Belize from the United Kingdom in 1981. Independence Day, celebrates the independence of Malta from the United Kingdom in 1964. International Day of Peace (International) National Pecan Cookie Day (United States) Acknowledgement of Earth, Wind, & Fire's "September" Student's Day (Bolivia) Victory over the Golden Horde in the Battle of Kulikovo (Russia) September 22 American Business Women's Day (United States) Dear Diary Day Hobbit Day, the containing week is celebrated as Tolkien Week. (American Tolkien Society) Independence Day, celebrates the independence of Bulgaria from the Ottoman Empire in 1908. Independence Day, celebrates the independence of Mali from France in 1960. OneWebDay, an annual day of Internet celebration and awareness, started in 2006. Resistance Fighting Day (Estonia) World Car-Free Day September 23 Celebrate Bisexuality Day Grito de Lares (Puerto Rico) Holocaust Memorial Day (Lithuania) Kyrgyz Language Day (Kyrgyzstan) National Day (Saudi Arabia) Teachers' Day (Brunei) September 24 Armed Forces Day (Peru) Constitution Day (Cambodia) La Mercè (Barcelona) Heritage Day (South Africa) Independence Day (Guinea-Bissau) Mahidol Day (Thailand) National Punctuation Day (United States) New Caledonia Day (New Caledonia) Republic Day (Trinidad and Tobago) September