diff --git a/imio_teleservices_templatetags/templatetags/imio_teleservices.py b/imio_teleservices_templatetags/templatetags/imio_teleservices.py
index aae3a08..3c51fb0 100644
--- a/imio_teleservices_templatetags/templatetags/imio_teleservices.py
+++ b/imio_teleservices_templatetags/templatetags/imio_teleservices.py
@@ -1,8 +1,10 @@
+import datetime
 import re
 from decimal import Decimal
 
 import requests
 from django import template
+from django.utils.safestring import SafeText
 
 from wcs.qommon import misc
 from wcs.qommon.templatetags.qommon import unlazy
@@ -10,6 +12,11 @@ from wcs.qommon.templatetags.qommon import unlazy
 register = template.Library()
 
 
+@register.filter
+def check_class(value):
+    return str(type(value))
+
+
 @register.filter
 def is_valid_belgian_nrn(value):
     return misc.validate_belgian_nrn(unlazy(value))
@@ -17,14 +24,43 @@ def is_valid_belgian_nrn(value):
 
 @register.filter
 def is_strong_authentication(session_user):
+    """
+    Anciennement town.py is_strong_authentication
+    session_user : session_user
+    return : (bool) True si le user est connecté avec une authentification forte
+    """
     return bool('_niss' in session_user.verified_fields)
 
 
+@register.filter
+def diff_dates(oldest_date, newest_date):
+    """
+    Anciennement town.py diff_dates
+    oldest_date : datetime ou SafeText sous la forme "jj/mm/aaaa" ou "aaaa-mm-jj" ou "jj-mm-aaaa"
+    newest_date : datetime ou SafeText sous la forme "jj/mm/aaaa" ou "aaaa-mm-jj" ou "jj-mm-aaaa"
+    return : (str) nombre de jours de différence entre les 2 dates
+    """
+    def transform_date(fdate):
+        if "/" in fdate:
+            return datetime.datetime.strptime(fdate, "%d/%m/%Y")
+        if "-" in fdate:
+            if len(fdate.split("-")[0]) == 4:
+                return datetime.datetime.strptime(fdate, "%Y-%m-%d")
+            if len(fdate.split("-")[0]) == 2:
+                return datetime.datetime.strptime(fdate, "%d-%m-%Y")
+    if type(oldest_date) == SafeText:
+        oldest_date = transform_date(oldest_date)
+    if type(newest_date) == SafeText:
+        newest_date = transform_date(newest_date)
+    diff = abs((oldest_date - newest_date).days)
+    return str(diff)
+
+
 @register.filter
 def liste_type_rdv_plusieurs_personnes(value):
     """
     Anciennement liste_type_general_rdv.py
-    value : (str) url api liste des type de rendez-vous
+    value : (str) url api liste des types de rendez-vous
     return : (list[str]) liste des différent type de rendez-vous sans - x personnes
     """
     headers = {'Accept': 'application/json'}