US Chess issues rating lists 12 times a year. Each list contains events rated since the most recent list.
In December we also issue the annual rating list, it contains everyone who played in an event that was rated in the last year.
As of September 1, 2013, the cutoff for a monthly ratings list is 11:45 PM Central Time on the 3rd Wednesday of the month before that list becomes official. For example, the October 2013 list will be created on Wednesday, September 18th. Events that have been received and rated by the cutoff are included in that ratings list.
However, even if someone isn’t in the most recently published ratings list, his or her last published rating is still current, even if it was published years ago. “Once Rated, Always Rated.”