Yes, JMT, you are correct, it is January. Unless you were looking at something other than a Gregorian Calendar.
As reported in the LVRJ 11/10/99, not that I believe everything I read:
In September <<The statewide win of $819.6 million was a 23.2 percent increase over the $665.5 million reported in September 1998, according to figures released Tuesday by the Nevada Gaming Control Board.
It surpassed the previous statewide record of $807.2 million set in January, which is historically the busiest month of the year for Nevada's hotel-casinos.>>