Located and added getDaysBetween().

git-svn-id: https://samskivert.googlecode.com/svn/trunk@1445 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/util/CalendarUtil.java

@@ -1,5 +1,5 @@
 //
-// $Id: CalendarUtil.java,v 1.1 2003/10/22 00:58:47 eric Exp $
+// $Id: CalendarUtil.java,v 1.2 2004/06/09 09:40:04 mdb Exp $
 
 package com.samskivert.util;
 
@@ -20,4 +20,35 @@ public class CalendarUtil
         cal.clear(Calendar.SECOND);
         cal.clear(Calendar.MILLISECOND);
     }
+
+    /**
+     * Returns the difference between the dates represented by the two
+     * calendars in days, properly accounting for daylight savings time,
+     * leap seconds, etc. The order of the two dates in time does not
+     * matter, the absolute number of days between them will be returned.
+     *
+     * @return the number of days between d1 and d2, 0 if they are the
+     * same day.
+     *
+     * @author http://www.jguru.com/forums/view.jsp?EID=489372
+     */
+    public static int getDaysBetween (Calendar d1, Calendar d2)
+    {
+        if (d1.after(d2)) {  // swap dates so that d1 is start and d2 is end
+            Calendar swap = d1;
+            d1 = d2;
+            d2 = swap;
+        }
+
+        int days = d2.get(Calendar.DAY_OF_YEAR) - d1.get(Calendar.DAY_OF_YEAR);
+        int y2 = d2.get(Calendar.YEAR);
+        if (d1.get(Calendar.YEAR) != y2) {
+            d1 = (Calendar)d1.clone();
+            do {
+                days += d1.getActualMaximum(Calendar.DAY_OF_YEAR);
+                d1.add(Calendar.YEAR, 1);
+            } while (d1.get(Calendar.YEAR) != y2);
+        }
+        return days;
+    }
 }