Hello,
Some companies are already having their drivers implement the rule changes to familiarize them with the new rules. However July 1, 2013 is the effective date of the new rules where a driver will be in violation if not following the new rule set. I have provided a link to the FMCSA website that states the enforceable date for the new rules. I hope this information helps, please let me know if you have any questions.
http://www.fmcsa.dot.gov/rules-regulations/topics/hos/index.htm
Have a great day.