Consider the following dates:
First date: 1963-10-18
Second date: 2013-10-11
This class returns the number of days as 18255 but the correct value is 18256.
The following site verifies this:
calendarhome.com/cgi-bin/date2.pl?m
...
And also Open Office Calc returns 18256 as the number of days between these two dates.