A joint issue is the issuance, by two or more countries, of similar stamps on the same date. The practice has become popular among postal authorities in recent years, and the stamps are becoming a popular collecting specialty. One popular way to collect these modern issues is on joint FDC.
November 20, 1910: The Start of the Mexican Revolution
The Mexican Revolution began in 1910, when a young politician named Francisco I. Madero declared his intent to run for president against long time dictator Porfirio Díaz. Afraid that the populist would win, Díaz imprisoned Madero, who escaped and wrote a well-publicized letter to the nation that called the Díaz regime illegal. Madero successfully called for a popular revolt against Díaz to begin on November 20.