diff --git a/organize/README.txt b/organize/README.txt
index b6bbd17..30c77b0 100644
--- a/organize/README.txt
+++ b/organize/README.txt
@@ -18,12 +18,15 @@ Let's start with a Person:
 
 A Person object knows the age of the person:
   
-  >>> john.age
-
+  >>> john.age is None
+  True
   >>> from datetime import date
   >>> john.birthDate = date(1980, 3, 25)
-  >>> john.age
+  >>> now = date(2006, 5, 12)
+  >>> john.ageAt(now)
   26
+  >>> john.age >= 26
+  True
 
   >>> john.firstName = u'John'
   >>> john.firstName
diff --git a/organize/party.py b/organize/party.py
index 7494217..5b49fa1 100644
--- a/organize/party.py
+++ b/organize/party.py
@@ -45,9 +45,12 @@ class Person(object):
 
     @property
     def age(self):
+        return self.ageAt(date.today())
+
+    def ageAt(self, date):
         if self.birthDate is None:
             return None
-        return int((date.today() - self.birthDate).days/365.25)
+        return int((date - self.birthDate).days/365.25)
 
 
 class Address(object):