Fallen 6 inches.
Due to leap years, it can vary, so it is every 5, 6 or 11 years. In recent times the 5th of May was a Saturday in 1984, 1990, 2001, 2007 and 2012, then next in 2018 and then 2029.
6 May 1950 was a Saturday.
May 6, 1967 fell on a Saturday.
May 6, 1972 fell on a Saturday.
May 6, 1911 fell on a Saturday.
May 6, 1989 fell on a Saturday.
May 6, 1995 fell on a Saturday.
April 6th falls on a Saturday this year - 2013.
No.
Your answer is in your question. You answered it yourself.
Every 6 years.