Added a more descriptive README

Author: mconfalonieri

.gitignore

@@ -1,3 +1,6 @@
+.DS_Store
+nb-configuration.xml
+nbproject/
 target/
 pom.xml.tag
 pom.xml.releaseBackup

README.md

@@ -1,2 +1,18 @@
-# plethonian-webapp
-Web application for Pletho's Calendar website
+# Plethonian Calendar Web Application
+
+An application that computes time according to the rules of the calendar
+introduces by Pletho, the Greek Platonic philosopher who was the real initiator
+of the Italian Renaissance.
+
+The website is visible at [Fasti Pletonis](https://fastipletonis.eu)
+
+## Rules of the calendar
+The calendar calculates months according to the Moon cycle, and years according
+to the Sun cycles, therefore the number of months in a year can be either
+twelve or thirteen, while the number of days in a month is either 29 or 30.
+These are the general rules:
+
+- each month starts at the first day AFTER the New Moon;
+- the year starts at the beginning of the first month AFTER the winter solstice;
+- each month is divided in four weeks, with one or two days outside the week
+cycle, depending if it's a 29-days or a 30-days month.