Of all September 1sts,...
14.25% are Sundays.
14.25% are Mondays.
14.5% are Tuesdays.
14% are Wednesdays.
14.5% are Thursdays.
14% are Fridays.
14.5% are Saturdays.
September is a whole months, so it couldn't have fallen on any day of the week. The first day of September (in 1994) was on Thursday, and the 30th was on a Friday.
September 1st 1969 was a Monday.
September 1st 1940 was a Sunday.
1st, September, 1729, was a Thursday.
September, 1st, 1956, was a Saturday.
September 1st, 1965 was on a Wednesday.
The 3rd of September 1939 was a Sunday.
Saturday
1st of September 2011 will be a Thursday.
Labor Day is always on the first Monday in September. It was on Monday September 3 in 2007.
The last day of September can be any day of the week
1st September 1989 fell on a Friday.