Friday the 13th etc.) of the year. Any month that starts on a Sunday contains a Friday the 13th, and there is at least one Friday the 13th in every calendar year. There can be as many as three Friday the 13ths in a single calendar year; either in February, March and November in a common year starting on Thursday (such as 2009, 2015 or 2026) (D), or January, April and July in a leap year starting on Sunday (such as 2012) (AG). The longest period that occurs without a Friday the 13th is 14 months, either from July to September the following
Black Friday (1978) guerrillas in Iran, who some believe were agitators. Black Friday is thought to have marked the point of no return for the revolution, and it led to the abolition of Iran's monarchy less than a year later. It is also believed that Black Friday played a crucial role in further radicalizing the protest movement, uniting the opposition to the Shah and mobilized the masses. Initially, opposition and western journalists claimed that the Iranian army had massacred thousands of protesters. The clerical leadership announced that "thousands have been massacred by Zionist troops". The events triggered protests that continued for another four