September 14, 1998 fell on a Monday.
Monday
As the 13th of September 1998 was the day before the 14th of September 1998, then the difference is minus one day.
14 September 1993 was a Tuesday.
14 September 2004 was a Tuesday.
September 14 1944 was a Thursday.
14 September 1958 was a Sunday.
September 14 2001 was a Friday.
September 14 1986 was a Sunday.
September 14 1978 was a Thursday.
September 14 1960 was a Wednesday.
September 14 1999 was a Tuesday.
September 14 2010 was a Tuesday.