diff --git a/lib/simple.js b/lib/simple.js
index 564bb9e..ca6fba1 100644
--- a/lib/simple.js
+++ b/lib/simple.js
@@ -27,7 +27,7 @@ function Simple() {
  */
 Simple.prototype._parse = function(str) {
 
-  var end = str.length;
+  var end = str.length,
       offset = 0;
 
   // There is a minimum length of 5 characters
diff --git a/lib/util.js b/lib/util.js
index 1cc776b..43feb5d 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -148,15 +148,12 @@ function addDuration(startDate, duration) {
     end.day += duration.getDays();
   }
   while(end.day && end.day > GlobalUtil.daysInMonth(end.month, end.year)) {
+    end.day -= GlobalUtil.daysInMonth(end.month, end.year);
     end.month += 1;
     if(end.month > 12) {
       end.month -= 12;
       end.year += 1;
     }
-    end.day -= GlobalUtil.daysInMonth(end.month, end.year);
-  }
-  if(end.day != undefined) {
-    endString = '-'+('00'+end.day).substr(-2,2)+endString;
   }
 
   if(duration.getMonths()) {
@@ -166,6 +163,19 @@ function addDuration(startDate, duration) {
     end.month -= 12;
     end.year += 1;
   }
+  // After readjusting the month, check again for days overflow
+  if(end.day && end.day > GlobalUtil.daysInMonth(end.month, end.year)){
+    end.day = end.day - GlobalUtil.daysInMonth(end.month, end.year);
+    end.month += 1;
+    if(end.month > 12) {
+      end.month -= 12;
+      end.year += 1;
+    }
+  }
+  
+  if(end.day != undefined) {
+    endString = '-'+('00'+end.day).substr(-2,2)+endString;
+  }
   if(end.month != undefined) {
     endString = '-'+('00'+end.month).substr(-2,2)+endString;
   }
@@ -254,12 +264,12 @@ function getDuration(startDate, endDate) {
 
   if(end.day != undefined) {
     while(end.day-start.day < 0) {
-      end.day += GlobalUtil.daysInMonth(end.month,end.year);
       end.month -= 1;
       if(end.month < 1) {
         end.year -= 1;
         end.month += 12;
       }
+      end.day += GlobalUtil.daysInMonth(end.month,end.year);
     }
     if(end.day-start.day > 0) {
       duration = ('00'+(end.day-start.day)).substr(-2,2)+'D'+duration;
diff --git a/test/range.js b/test/range.js
index 99e0805..de89403 100644
--- a/test/range.js
+++ b/test/range.js
@@ -125,7 +125,6 @@ describe('Range', function(){
 
     it('should calculate range correctly', function(){
       var range = new Range('+1000-02-03/+2000');
-
       expect(range.duration.getYears()).to.equal(999);
       expect(range.duration.getMonths()).to.equal(10);
       expect(range.duration.getDays()).to.equal(29);
@@ -133,15 +132,20 @@ describe('Range', function(){
 
     it('should calculate tricky range correctly', function(){
       var range = new Range('+1970-01-31/+1973-02-01');
-
-      expect(range.duration.getYears()).to.equal(2);
-      expect(range.duration.getMonths()).to.equal(11);
-      expect(range.duration.getDays()).to.equal(29);
+      expect(range.duration.getYears()).to.equal(3);
+      expect(range.duration.getMonths()).to.equal(undefined);
+      expect(range.duration.getDays()).to.equal(1);
+    });
+    
+    it('should calculate days correctly', function(){
+      var range = new Range('+1999-02-28/+1999-03-01');
+      expect(range.duration.getYears()).to.not.exist;
+      expect(range.duration.getMonths()).to.not.exist;
+      expect(range.duration.getDays()).to.equal(1);
     });
 
     it('should calculate approximate duration', function(){
       var range = new Range('A+1000/P1000Y');
-
       expect(range.end.getYear()).to.equal(2000);
       expect(range.isApproximate()).to.equal(true);
     });
diff --git a/test/util.js b/test/util.js
index 0b8b0ea..6466255 100644
--- a/test/util.js
+++ b/test/util.js
@@ -235,6 +235,25 @@ describe('Util', function(){
       }).to.throw(Error, 'New date out of range');
 
     });
+    
+    it('should handle simple month overflow', function(){
+      var start = new Simple('+1707-02-28'),
+          duration = new Duration('P1D'),
+          end = GedcomXDate.addDuration(start, duration);
+          
+       expect(end.getYear()).to.equal(1707);
+       expect(end.getMonth()).to.equal(3);
+       expect(end.getDay()).to.equal(1);
+    });
+    
+    it('complex case', function(){
+      var start = new Simple('+1771-08-30'),
+          duration = new Duration('P1M1D'),
+          end = GedcomXDate.addDuration(start, duration);
+      expect(end.getYear()).to.equal(1771);
+      expect(end.getMonth()).to.equal(10);
+      expect(end.getDay()).to.equal(1);
+    })
 
   });
 
@@ -309,6 +328,21 @@ describe('Util', function(){
       expect(duration.getSeconds()).to.equal(undefined);
 
     });
+    
+    it('should overflow days when months are not the same length', function(){
+      
+      var start = new Simple('+0999-11-30T00:00:00'),
+          end = new Simple('+0999-12-01T00:00:00'),
+          duration = GedcomXDate.getDuration(start, end);
+          
+      expect(duration.getYears()).to.equal(undefined);
+      expect(duration.getMonths()).to.equal(undefined);
+      expect(duration.getDays()).to.equal(1);
+      expect(duration.getHours()).to.equal(undefined);
+      expect(duration.getMinutes()).to.equal(undefined);
+      expect(duration.getSeconds()).to.equal(undefined);
+      
+    });
 
     it('should overflow months', function(){