restrict dates less than the current date

message.xml

@@ -6,5 +6,8 @@ this repository contains the full copyright notices and license terms. -->
         <record model="ir.message" id="msg_no_parties">
             <field name="text">There is not parties.</field>
         </record>
+        <record model="ir.message" id="msg_birthday">
+            <field name="text">The birthdate shouldn't be greater than today's date.</field>
+        </record>
     </data>
 </tryton>

party.py

@@ -1,6 +1,6 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
-from datetime import datetime
+from datetime import datetime, date
 from trytond.i18n import gettext
 from trytond.model import fields, ModelSQL, ModelView
 from trytond.pool import PoolMeta, Pool
@@ -89,6 +89,14 @@ class Party(metaclass=PoolMeta):
     second_family_name = fields.Char('Segundo Apellido')
     city_document_exp = fields.Char('City of Document Expedition ID')
 
+    @classmethod
+    def validate(cls, parties):
+        for party in parties:
+            if party.birthday and party.birthday > date.today():
+                raise UserError(gettext('party_personal.msg_birthday'))
+        parties = super(Party, cls).validate(parties)
+        return parties
+
     @fields.depends('bmi', 'bmi_category')
     def on_change_bmi(self):
         if self.bmi: