An effective date or as of date is the date upon which something is considered to take effect. This may be different from the date upon which the event actually occurs or is recorded. It is normally used by people with a poor grasp of the English language. In most cases the word "In" is preferable. For example, "As of 2009, there were 20 houses on the site ...", should be, "In 2009, there were 20 houses on the site ...". The latter, is obviously correct English and the "As of-isms" define a low type of slang used by sports reporters.