date object: Manipulate and format dates

This class can manipulate dates in several ways and format a date using words and conventions of your language.

It is possible to compute the difference between 2 dates in days, hours, minutes, seconds.

You can also add or subtract a period value of days, hours, years, ... and return the resulting date in a textual representation.

There are also other useful methods to get common information, like the day of the week, days in month, day of year, or to comparing two dates.