Companies that are subject to the Investment Act of 1940 have to report their quarter end holdings and compute the net asset value of the fund. These were the numbers on September 30, and things may have looked very different on October 1. These figures don't get updated again until Dec 31, and those reports aren't due until the funds file their annual report, about 75 days after year end as I recall.
This is for funds and such, but not so for the individuals. Officers and directors have to report transactions with a few days.