diff --git a/kfet/statistic.py b/kfet/statistic.py
index 4ae17959..fe948f73 100644
--- a/kfet/statistic.py
+++ b/kfet/statistic.py
@@ -1,9 +1,9 @@
 # -*- coding: utf-8 -*-
 
-import ast
 from datetime import date, datetime, time, timedelta
 
 from dateutil.relativedelta import relativedelta
+from dateutil.parser import parse as dateutil_parse
 
 from django.utils import timezone
 from django.db.models import Sum
@@ -114,25 +114,29 @@ class MonthScale(Scale):
         return to_kfet_day(dt).replace(day=1)
 
 
-def stat_manifest(scales_def=None, scale_args=None, **url_params):
+def stat_manifest(scales_def=None, scale_args=None, scale_prefix=None,
+                  **other_url_params):
+    if scale_prefix is None:
+        scale_prefix = 'scale_'
     if scales_def is None:
         scales_def = []
     if scale_args is None:
         scale_args = {}
-    return [
-        dict(
+    manifest = []
+    for label, cls in scales_def:
+        url_params = {scale_prefix+'name': cls.name}
+        url_params.update({scale_prefix+key: value
+                           for key, value in scale_args.items()})
+        url_params.update(other_url_params)
+        manifest.append(dict(
             label=label,
-            url_params=dict(
-                scale=cls.name,
-                scale_args=scale_args,
-                **url_params,
-            ),
-        )
-        for label, cls in scales_def
-    ]
+            url_params=url_params,
+        ))
+    return manifest
 
 
-def last_stats_manifest(scales_def=None, scale_args=None, **url_params):
+def last_stats_manifest(scales_def=None, scale_args=None, scale_prefix=None,
+                        **url_params):
     scales_def = [
         ('Derniers mois', MonthScale, ),
         ('Dernières semaines', WeekScale, ),
@@ -145,7 +149,7 @@ def last_stats_manifest(scales_def=None, scale_args=None, **url_params):
         n_steps=7,
     ))
     return stat_manifest(scales_def=scales_def, scale_args=scale_args,
-                         **url_params)
+                         scale_prefix=scale_prefix, **url_params)
 
 
 # Étant donné un queryset d'operations
@@ -156,20 +160,61 @@ def tot_ventes(queryset):
 
 
 class ScaleMixin(object):
+    scale_args_prefix = 'scale_'
+
+    def get_scale_args(self, params=None, prefix=None):
+        """Retrieve scale args from params.
+
+        Should search the same args of Scale constructor.
+
+        Args:
+            params (dict, optional): Scale args are searched in this.
+                Default to GET params of request.
+            prefix (str, optional): Appended at the begin of scale args names.
+                Default to `self.scale_args_prefix`.
+
+        """
+        if params is None:
+            params = self.request.GET
+        if prefix is None:
+            prefix = self.scale_args_prefix
+
+        scale_args = {}
+
+        name = params.get(prefix+'name', None)
+        if name is not None:
+            scale_args['name'] = name
+
+        n_steps = params.get(prefix+'n_steps', None)
+        if n_steps is not None:
+            scale_args['n_steps'] = int(n_steps)
+
+        begin = params.get(prefix+'begin', None)
+        if begin is not None:
+            scale_args['begin'] = dateutil_parse(begin)
+
+        end = params.get(prefix+'send', None)
+        if end is not None:
+            scale_args['end'] = dateutil_parse(end)
+
+        last = params.get(prefix+'last', None)
+        if last is not None:
+            scale_args['last'] = (
+                last in ['true', 'True', '1'] and True or False)
+
+        return scale_args
 
     def get_context_data(self, *args, **kwargs):
         context = super().get_context_data(*args, **kwargs)
 
-        scale_name = self.request.GET.get('scale', None)
+        scale_args = self.get_scale_args()
+        scale_name = scale_args.pop('name', None)
+        scale_cls = Scale.by_name(scale_name)
 
-        cls = Scale.by_name(scale_name)
-        if cls is None:
+        if scale_cls is None:
             scale = self.get_default_scale()
         else:
-            scale_args = self.request.GET.get('scale_args', {})
-            if isinstance(scale_args, str):
-                scale_args = ast.literal_eval(scale_args)
-            scale = cls(**scale_args)
+            scale = scale_cls(**scale_args)
 
         self.scale = scale
         context['labels'] = scale.get_labels()
diff --git a/requirements.txt b/requirements.txt
index 06f6c46e..ce081588 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -20,3 +20,4 @@ django-widget-tweaks==1.4.1
 git+https://git.eleves.ens.fr/cof-geek/django_custommail.git#egg=django_custommail
 ldap3
 git+https://github.com/Aureplop/channels.git#egg=channels
+python-dateutil