Change error return values and fixed one error case of DATE_PARSE

V3.1: Changed the return values on error, and fixed one case of parsing error

V3.0
Date management was enhanced in Libre Office, so did we in this Milesian package.

One major difference: whereas OpenOffice uses "reverse" year counting system,, i.e. year -1 comes just before year 1, the Milesian date parser (DATE_PARSE) uses integer year counting system, i.e. there is a year 0 just before year 1, whether the calendar is Julian or Milesian.