The USGS has released an upated "Divisions of Geologic Time" produced by the USGS Geologic Names Committee and the Association of American State Geologists (AASG), which represents an update containing the unit names and boundary age estimates ratified by the International Commission on Stratigraphy (ICS).
The fact sheet states that scientists should note that other published time scales may be used, provided that these are specified and referenced (for example, Palmer, 1983; Harland and others, 1990; Haq and Eysinga, 1998; Gradstein and others, 2004; Ogg and others, 2008).
USGS FS 2010-3059: Divisions of Geologic Time - Major Chronostratigraphic and Geochronologic Units http://pubs.usgs.gov/fs/2010/3059/
This fact sheet is a modification of USGS Fact Sheet 2007–3015 by the U.S. Geological Survey Geologic Names Committee.