Tuesday
August 9th, 1979 fell on a Thursday.
July 9th 1977 was a Saturday.
December 9th, 1977 was on a Friday.
The 9th of August can occur on any day of the week. As the question was asked in July 2014, it is possible you were referring to August of 2014, in which case the answer is Saturday.
August 15th 1977 was a Monday.
August 13 1977 was a Saturday.
August 19 1977 was on a Friday.
August 8th 1977 was a Monday.
August 5 1977 was a Friday.
August 10, 1977 was a Wednesday.
Thursday
its on a Monday!