If he's specifically interested in just the number of days, then yes you're correct it's not a solution (hence the "Possibly" :). However if the actual problem is showing a duration in a hyooman friendly representation that module is capable of normalizing a duration into the smallest possible units of each (and its logic in doing so using a base date may be of use figuring out how to approach the problem if the actual number of days is the real goal; the section on normalization in the docs mentions it under "Months of unequal length").