The United States Citizenship and Immigration Services (USCIS) publishes a monthly report on processing times at its service centers. The processing dates represent the receipt dates of petitions and applications currently being processed by the USCIS Service Center (Texas, Nebraska, California and Vermont), USCIS field offices, and the National Benefits Center.
If a type of application is being completed within USCIS target timeframes, the timeframe will be shown. For example, USCIS sets a goal to complete I-131 Travel Document applications within three months, and the service center is indeed processing those cases within three months, so the processing report will show "3 months."
If a USCIS service center doesn't meet the target timeframe, a date will be shown. In the above example, if a particular service center cannot complete I-131 cases within three months, it will publish a date (January 1, 2009) to indicate what cases they are currently processing.
For PERM Labor Certification Applications, please see Current PERM Processing Times.