diff --git a/app/__init__.py b/app/__init__.py
index 86646eb407..f1fba060a4 100755
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -148,7 +148,7 @@ def handle_invalid_usage(error):
 
 # JSON ENCODING
 # used by some internal finctions
-# the API is now using flask_son, NOT THIS ENCODER
+# the API is now using flask_json, NOT THIS ENCODER
 class ScoDocJSONEncoder(json.JSONEncoder):
     def default(self, o):  # pylint: disable=E0202
         if isinstance(o, (datetime.date, datetime.datetime)):
@@ -260,7 +260,13 @@ def create_app(config_class=DevConfig):
 
     CAS(app, url_prefix="/cas", configuration_function=cas.set_cas_configuration)
     app.wsgi_app = ReverseProxied(app.wsgi_app)
-    FlaskJSON(app)
+    app_json = FlaskJSON(app)
+
+    @app_json.encoder
+    def scodoc_json_encoder(o):
+        "Overide default date encoding (RFC 822) and use ISO"
+        if isinstance(o, (datetime.date, datetime.datetime)):
+            return o.isoformat()
 
     # Pour conserver l'ordre des objets dans les JSON:
     # e.g. l'ordre des UE dans les bulletins
diff --git a/tests/api/test_api_etudiants.py b/tests/api/test_api_etudiants.py
index 56f3193d33..c7d948ef2a 100644
--- a/tests/api/test_api_etudiants.py
+++ b/tests/api/test_api_etudiants.py
@@ -17,6 +17,7 @@ Utilisation :
         pytest tests/api/test_api_etudiants.py
 """
 
+import re
 import requests
 from app.scodoc import sco_utils as scu
 
@@ -100,6 +101,7 @@ def test_etudiants_courant(api_headers):
 
     etud = etudiants[-1]
     assert verify_fields(etud, ETUD_FIELDS) is True
+    assert re.match(r"^\d{4}-\d\d-\d\d$", etud["date_naissance"])
 
 
 def test_etudiant(api_headers):