Example: If a form for claiming sickness benefits is mailed to an employee on July 13, for the period from July 1 to July 14, the employee must file the claim within 30 days after July 14 [on or before August 13], to be paid benefits for the period July 1 to July 14. If the claim form was not mailed to the employee until July 16, the claim must be filed within 30 days after July 16 [on or before August 15].
20 C.F.R. §335.4