Taking from the start of the 20th century, the 5th of May was a Wednesday in 1909, 1915, 1920, 1926, 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999, 2004 and 2010. It will next happen in 2021.
Within any 4 year period, there is always a leap year. That causes a day to be skipped. So after 4 years, a date will be on a day 5 days after the one it was on 4 years before that. Wednesday is 5 days after Friday, so if a date is on a Friday, 4 years later it will be on a Wednesday.
Wednesday
It was a Wednesday
July 5 1989 was a Wednesday.
September 5 1984 was a Wednesday.
May 5 2010 was a Wednesday.
It is the way calendars work. Friday is 5 days after Sunday, but there will be at least one leap year in that period, which means one day will be skipped, so it only takes 4 years to reach Friday. That same pattern continues, in that although Wednesday is 5 days later, it will come round in 4 years due to a leap year. Yet again, Monday is 5 years after Wednesday, but the leap year will make it only take 4 years to come round. There are many patterns like that in calendar dates.
The Wednesday was skipped over due to the leap year in 1940. It was on a Tuesday in 1939. As 1940 was a leap year, it skipped over the Wednesday, and it was on a Thursday. It was not until 1945 that Wednesday came round again. Between 1934 and 1945 is an 11 year gap. That length of time without a date occurring on the same day is very common. A date happens on the same day again every 5, 6 or 11 years. It depends on how the leap years fall in the period.
December 5th 1979 was a Wednesday.
In a 28-year cycle, starting in 1984 and ending in 2011, May 5 fell on a Saturday in the years: 1984 1990 2001 2006 For further years in which May 5 falls on a Saturday, add 28 to these years.
It was a Wednesday.
It was a Wednesday.