diff --git a/Personnummer/Personnummer.cs b/Personnummer/Personnummer.cs
index af4689c..31230c3 100644
--- a/Personnummer/Personnummer.cs
+++ b/Personnummer/Personnummer.cs
@@ -24,7 +24,15 @@ public Options()
 
         public DateTime Date { get; private set; }
 
-        public int Age => DateTime.Now.Year - Date.Year;
+        public int Age
+        {
+            get
+            {
+                var now = DateTime.Now;
+                var differenceInTotalMonth = 12 * (now.Year - Date.Year) + now.Month - Date.Month;
+                return differenceInTotalMonth / 12;
+            }
+        }
 
         public string Separator => Age >= 100 ? "+" : "-";