diff --git a/src/fiber_package/entity/person.py b/src/fiber_package/entity/person.py
index 9c4019e..4d05c34 100644
--- a/src/fiber_package/entity/person.py
+++ b/src/fiber_package/entity/person.py
@@ -27,14 +27,13 @@ class PersonModel(FiberBaseModel):
     date_of_birth: date | None = None
 
 
-    @computed_field # type: ignore[prop-decorator]
-    @property
-    def underage(self) -> bool:
+    def is_underage(self, ref_date: date | None = None) -> bool | None:
         if self.date_of_birth is None:
             return False
-        today = date.today()
-        age = ( today.year - self.date_of_birth.year
-                - ( (today.month, today.day)
+        if ref_date is None:
+            ref_data = date.today()
+        age = ( ref_date.year - self.date_of_birth.year
+                - ( (ref_date.month, ref_date.day)
                     < (self.date_of_birth.month, self.date_of_birth.day) )
             )
         return age < 18