Could you please help me understand the following sentence?

The operator, needless to say, was happy to eat his words. The owner of the real estate however, was convinced that I'd pulled a fast one him. I don't think a day of that twenty-year lease passed that he didn't wish he'd demanded a lot more.

Does the underlined phrase mean : Any day in the period during which the lease was valid.?

Thank you very much in advance.
You are right.

Every day of the twenty-year period he wished he had demanded a lot more.

Thank you very much Rover for your help.