diff --git a/Personnummer.Tests/PersonnummerTests.cs b/Personnummer.Tests/PersonnummerTests.cs
index 527e458..4428084 100644
--- a/Personnummer.Tests/PersonnummerTests.cs
+++ b/Personnummer.Tests/PersonnummerTests.cs
@@ -236,5 +236,15 @@ public void TestParseTooShort()
                 }).Message
             );
         }
+
+        [Fact]
+        public void TestEdgeCasesAroundBirthday()
+        {
+            var timeProvider = new TestTimeProvider(); //TestTime is 2025-10-05 
+            Assert.Equal(18, new Personnummer("20071004-3654", new Personnummer.Options() {TimeProvider = timeProvider} ).Age); // Had birthday yesterday
+            Assert.Equal(18, new Personnummer("20071005-3653", new Personnummer.Options() {TimeProvider = timeProvider} ).Age); // Birthday today
+            Assert.Equal(17, new Personnummer("20071006-3652", new Personnummer.Options() {TimeProvider = timeProvider} ).Age); // Upcoming Birthday tomorrow
+        }
+       
     }
 }
diff --git a/Personnummer/Personnummer.cs b/Personnummer/Personnummer.cs
index 1d8a9a1..637b5f1 100644
--- a/Personnummer/Personnummer.cs
+++ b/Personnummer/Personnummer.cs
@@ -46,7 +46,10 @@ public int Age
                 var now = _options.DateTimeNow;
                 var age = now.Year - Date.Year;
 
-                if (now.Month >= Date.Month && now.Day >= Date.Day)
+                var hadBirthdayThisYear = (now.Month > Date.Month) ||
+                                        (now.Month == Date.Month && now.Day >= Date.Day);
+
+                if (!hadBirthdayThisYear)
                 {
                     age--;
                 }