I'm not sure of the formatting of your information, but let's assume you have 66.5 in cell A1. In cell B1, enter the following =A1/8.
Right click on cell B1 and change the format to Custom. In the "Type:" field at the top, enter dd:hh:mm and click OK.
You should be left with 08:07:30, which is 8 Days, 7 hours, and 30 minutes.