Time & Date I need this "Dates" page as a general page for the top of my Dates Menu. Will add more information about dates as I find useful stuff on the internet. In the meantime, just below here is a drop down menu which gives you links to the stuff already on my website
I suspect you are using a DateTime field to store a duration. As long as the duration doesn't exceed 24 hours you'll be fine. But the DateTime field is intended to show a point in time so once you have more than 24 hours, you end up with days as well so the calculation no longer works. 1.475 * 60 = 88.5 minutes rather than 1468.5.. And if you were to display the value as a date, it would be 12/30/1899 00:28:30.
So, could the duration ever be more than 24 hours?