The Day of Arafah (also referred to as the Day of Repentance) is an Islamic festival celebrated on the ninth day of the month of Dhu al-Hijjah. It is the second day of the Hajj, an annual pilgrimage to Mecca.
Programmers' Day is an international professional day celebrated on the 256th day of the year. It falls on September 13 during common years and September 12 during leap years. The holiday is observed in many countries, but Russia is the only country where it is recognized officially.
Mindfulness Day is an annual event held on September 12. It was created by Wisdom Publications, a publisher of Buddhist books and practical works on mindfulness.
Saint Patrick's Battalion Remembrance Day is observed in Mexico on September 12. It honors the immigrants and expatriates of European descent (mostly Irish) who fought on the side of Mexico during the Mexican-American War and were hanged by American soldiers.
September 12 is United Nations Day for South-South Cooperation. This observance was officially established in December 2003. It was originally observed on December 19, but in 2011 the date was moved to September 12.