Medicare can be backdated to the first of the month dialysis started IF self-dialysis training starts prior to the first day of the third full month of dialysis. The patient's training started too late to get backdating. Therefore, the first date that he/she would be eligible for Medicare would be October 1. The Medicare secondary payer clock starts on the date the patient is first eligible for Medicare, whether or not he/she enrolls. In this patient's case, the COB clock would start October 1.