Original:  The new warnings will come into effect January 2007 but the manufacturers will not have to produce the new warnings until February 27, 2008 and  August 2008 for retailers to clear all their old stock.
Revised:  The new warnings will come into effect January 2007 but the manufacturers will not have to produce the new warnings until February 27, 2008 and August 2008 to clear all their old stock.
Edit intent: style