On Saturday at 1 PM, Bill opens his Behavior Analysis text b…

On Saturday at 1 PM, Bill opens his Behavior Analysis text by Cooper, Heron, and Heward and begins to read.  At 3 PM, he stops reading and closes the book.  He does not open it again to read until the next day at 5 PM.  From this information, we measure a dimensional quantity of 26 hours.  Which dimensional quantity did we measure?