8.5 times
Since 1948, Easter Sunday has fallen in 1999 and 2010. Easter Sunday will next fall on April 4 in 2021.
Including 1948, there have been 10 of them. They were in 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999, 2004 and 2010.
12 times in the years 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999, 2004 and 2010. The next one will be in 2021.
Nine times since 1949 counting this year.
As of 2011, the last time Good Friday fell on April 20 was in 1957. (Bobo192) Bobo192's answer is incorrect. Good Friday in 1957 was not on April 20. It was actually on April 19. Since 1901, Good Friday has fallen on the 20th of April in the years 1962, 1973 and 1984. So with that said, 1984 was the last year Good Friday was on the 20th. The next time it will fall on April 20 will be in 2057 and then again in 2068. As an FYI, Easter Sunday is set to fall on April 20 in 2014 (and again in 2025).
Since 1873, August 13 has fallen on a Friday 17 times. The occurrences are in the years: 1874, 1880, 1886, 1891, 1897, 1908, 1915, 1920, 1926, 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, and 2021. The pattern can be determined using a perpetual calendar or a software tool for date calculations.
April 12 1948 was a Monday.
September 10, 1948 fell on a Friday.
July 2 1948 was a Friday.
June 25, 1948, was a Friday.
October 8 1948 was a Friday.
17 April 1948 was a Saturday.