This Good Friday is not simply the most solemn day in the Christian calendar but a convergence of movable feasts that doesn't occur more than once in a century. March 21 is also the first day of the Jewish festival of Purim and the celebration of the birth of the prophet Muhammed. The three holidays have fallen on the same day only nine times in 800 years, Time reports.
In addition, today is also the Persian New Year, a holy day for Buddhists in Thailand, and the eve of the riotous Hindu festival of Holi. "Half the world's population is going to be celebrating something," said one professor of religion. Thanks to the use of different calendars, today's overlapping of holidays from across the world's religions shouldn't occur more than once a millennium.