The phrase "week of the 9th" typically refers to the week during which the 9th day of a month occurs. This could mean the week starting on the Sunday before the 9th or the Monday of that week, depending on context. It is often used in scheduling or planning to specify a particular timeframe.
9th January 2010 was a Saturday.
The 9th of May 1851 was a Friday.
9th May 1948 was a Sunday.
9th February 1999, was a Tuesday.
January 9th, 1900 was a Tuesday.
It was a Sunday.
August 9th, 1979 fell on a Thursday.
December 9th, 1950 fell on a Saturday.
it was a Tuesday
October 9th, 1997 fell on a Thursday.
February 9th, 1939 fell on a Thursday.
December 9th, 2011 fell on a Friday.