From the California Chamber of Commerce:
The San Francisco Board of Supervisors has adopted an ordinance providing for a “transition period” for implementation of the sick pay ordinance that became effective February 5, 2007.The transition period was adopted in recognition of the uncertainty generated by the ordinance making it difficult for employers to know how to comply.
The transition period runs from February 5, 2007 through June 5, 2007, during which employers are required to accrue hours and keep all records required by the program. Employers are given the option of delaying payment of sick leave benefits under the program until June 6, 2007, with no interest accruing on any delayed benefits. No penalties may be assesed against an employer for failure to pay such benefits during the transition period. Other aspects of the original ordinance, including protection for employees from adverse action for exercising protected rights, are enforcible.
The full ordinance can be found here