diff --git a/kfet/static/kfet/js/statistic.js b/kfet/static/kfet/js/statistic.js
index f210c11d..db31e0e8 100644
--- a/kfet/static/kfet/js/statistic.js
+++ b/kfet/static/kfet/js/statistic.js
@@ -61,7 +61,7 @@
                 var chart = charts[i];
 
                 // format the data
-                var chart_data =  is_time_chart ? handleTimeChart(chart.values) : dictToArray(chart.values, 1);
+                var chart_data =  is_time_chart ? handleTimeChart(chart.values) : dictToArray(chart.values, 0);
 
                 chart_datasets.push(
                     {
@@ -132,7 +132,7 @@
                     type: 'line',
                     options: chart_options,
                     data: {
-                        labels: (data.labels || []).slice(1),
+                        labels: data.labels || [],
                         datasets: chart_datasets,
                     }
                 };
diff --git a/kfet/statistic.py b/kfet/statistic.py
index fe948f73..5ff169ff 100644
--- a/kfet/statistic.py
+++ b/kfet/statistic.py
@@ -4,6 +4,7 @@ from datetime import date, datetime, time, timedelta
 
 from dateutil.relativedelta import relativedelta
 from dateutil.parser import parse as dateutil_parse
+import pytz
 
 from django.utils import timezone
 from django.db.models import Sum
@@ -13,7 +14,8 @@ KFET_WAKES_UP_AT = time(7, 0)
 
 def kfet_day(year, month, day, start_at=KFET_WAKES_UP_AT):
     """datetime wrapper with time offset."""
-    return datetime.combine(date(year, month, day), start_at)
+    naive = datetime.combine(date(year, month, day), start_at)
+    return pytz.timezone('Europe/Paris').localize(naive, is_dst=None)
 
 
 def to_kfet_day(dt, start_at=KFET_WAKES_UP_AT):
@@ -32,16 +34,21 @@ class Scale(object):
         self.std_chunk = std_chunk
         if last:
             end = timezone.now()
+        if std_chunk:
+            if begin is not None:
+                begin = self.get_chunk_start(begin)
+            if end is not None:
+                end = self.do_step(self.get_chunk_start(end))
 
         if begin is not None and n_steps != 0:
-            self.begin = self.get_from(begin)
+            self.begin = begin
             self.end = self.do_step(self.begin, n_steps=n_steps)
         elif end is not None and n_steps != 0:
-            self.end = self.get_from(end)
+            self.end = end
             self.begin = self.do_step(self.end, n_steps=-n_steps)
         elif begin is not None and end is not None:
-            self.begin = self.get_from(begin)
-            self.end = self.get_from(end)
+            self.begin = begin
+            self.end = end
         else:
             raise Exception('Two of these args must be specified: '
                             'n_steps, begin, end; '
@@ -71,7 +78,7 @@ class Scale(object):
     def get_datetimes(self):
         datetimes = [self.begin]
         tmp = self.begin
-        while tmp <= self.end:
+        while tmp < self.end:
             tmp = self.do_step(tmp)
             datetimes.append(tmp)
         return datetimes
@@ -232,3 +239,87 @@ class ScaleMixin(object):
             qs.filter(**{begin_f: begin, end_f: end})
             for begin, end in scale
         ]
+
+    def get_by_chunks(self, qs, scale, field_callback=None, field_db='at'):
+        """Objects of queryset ranked according to a given scale.
+
+        Returns a generator whose each item, corresponding to a scale chunk,
+        is a generator of objects from qs for this chunk.
+
+        Args:
+            qs: Queryset of source objects, must be ordered *first* on the
+                same field returned by `field_callback`.
+            scale: Used to rank objects.
+            field_callback: Callable which gives value from an object used
+                to compare against limits of the scale chunks.
+                Default to: lambda obj: getattr(obj, field_db)
+            field_db: Used to filter against `scale` limits.
+                Default to 'at'.
+
+        Examples:
+            If queryset `qs` use `values()`, `field_callback` must be set and
+                could be: `lambda d: d['at']`
+            If `field_db` use foreign attributes (eg with `__`), it should be
+                something like: `lambda obj: obj.group.at`.
+
+        """
+        if field_callback is None:
+            def field_callback(obj):
+                return getattr(obj, field_db)
+
+        begin_f = '{}__gte'.format(field_db)
+        end_f = '{}__lte'.format(field_db)
+
+        qs = (
+            qs
+            .filter(**{begin_f: scale.begin, end_f: scale.end})
+        )
+
+        obj_iter = iter(qs)
+
+        last_obj = None
+
+        def _objects_until(obj_iter, field_callback, end):
+            """Generator of objects until `end`.
+
+            Ends if objects source is empty or when an object not verifying
+            field_callback(obj) <= end is met.
+
+            If this object exists, it is stored in `last_obj` which is found
+            from outer scope.
+            Also, if this same variable is non-empty when the function is
+            called, it first yields its content.
+
+            Args:
+                obj_iter: Source used to get objects.
+                field_callback: Returned value, when it is called on an object
+                    will be used to test ordering against `end`.
+                end
+
+            """
+            nonlocal last_obj
+
+            if last_obj is not None:
+                yield last_obj
+                last_obj = None
+
+            for obj in obj_iter:
+                if field_callback(obj) <= end:
+                    yield obj
+                else:
+                    last_obj = obj
+                    return
+
+        for begin, end in scale:
+            # forward last seen object, if it exists, to the right chunk,
+            # and fill with empty generators for intermediate chunks of scale
+            if last_obj is not None:
+                if field_callback(last_obj) > end:
+                    yield iter(())
+                    continue
+
+            # yields generator for this chunk
+            # this set last_obj to None if obj_iter reach its end, otherwise
+            # it's set to the first met object from obj_iter which doesn't
+            # belong to this chunk
+            yield _objects_until(obj_iter, field_callback, end)
diff --git a/kfet/templates/kfet/article_read.html b/kfet/templates/kfet/article_read.html
index 6fe025f6..19a11094 100644
--- a/kfet/templates/kfet/article_read.html
+++ b/kfet/templates/kfet/article_read.html
@@ -104,7 +104,7 @@
 $(document).ready(function() {
     var stat_last = new StatsGroup(
         "{% url 'kfet.article.stat.sales.list' article.id %}",
-        $("#stat_last"),
+        $("#stat_last")
     );
 });
 </script>
diff --git a/kfet/views.py b/kfet/views.py
index cfc58aa0..1df78d1e 100644
--- a/kfet/views.py
+++ b/kfet/views.py
@@ -2369,13 +2369,19 @@ class AccountStatOperation(ScaleMixin, PkUrlMixin, JSONDetailView):
         # à l'article en question et qui ne sont pas annulées
         # puis on choisi pour chaques intervalle les opérations
         # effectuées dans ces intervalles de temps
-        all_operations = (Operation.objects
-                          .filter(group__on_acc=self.object)
-                          .filter(canceled_at=None)
-                          )
+        all_operations = (
+            Operation.objects
+            .filter(group__on_acc=self.object,
+                    canceled_at=None)
+            .values('article_nb', 'group__at')
+            .order_by('group__at')
+        )
         if types is not None:
             all_operations = all_operations.filter(type__in=types)
-        chunks = self.chunkify_qs(all_operations, scale, field='group__at')
+        chunks = self.get_by_chunks(
+            all_operations, scale, field_db='group__at',
+            field_callback=(lambda d: d['group__at']),
+        )
         return chunks
 
     def get_context_data(self, *args, **kwargs):
@@ -2391,7 +2397,8 @@ class AccountStatOperation(ScaleMixin, PkUrlMixin, JSONDetailView):
         # On compte les opérations
         nb_ventes = []
         for chunk in operations:
-            nb_ventes.append(tot_ventes(chunk))
+            ventes = sum(ope['article_nb'] for ope in chunk)
+            nb_ventes.append(ventes)
 
         context['charts'] = [{"color": "rgb(255, 99, 132)",
                               "label": "NB items achetés",
@@ -2442,29 +2449,39 @@ class ArticleStatSales(ScaleMixin, JSONDetailView):
         context = {'labels': old_ctx['labels']}
         scale = self.scale
 
-        # On selectionne les opérations qui correspondent
-        # à l'article en question et qui ne sont pas annulées
-        # puis on choisi pour chaques intervalle les opérations
-        # effectuées dans ces intervalles de temps
-        all_operations = (
+        all_purchases = (
             Operation.objects
-            .filter(type=Operation.PURCHASE,
-                    article=self.object,
-                    canceled_at=None,
-                    )
+            .filter(
+                type=Operation.PURCHASE,
+                article=self.object,
+                canceled_at=None,
+            )
+            .values('group__at', 'article_nb')
+            .order_by('group__at')
         )
-        chunks = self.chunkify_qs(all_operations, scale, field='group__at')
+        liq_only = all_purchases.filter(group__on_acc__trigramme='LIQ')
+        liq_exclude = all_purchases.exclude(group__on_acc__trigramme='LIQ')
+
+        chunks_liq = self.get_by_chunks(
+            liq_only, scale, field_db='group__at',
+            field_callback=lambda d: d['group__at'],
+        )
+        chunks_no_liq = self.get_by_chunks(
+            liq_exclude, scale, field_db='group__at',
+            field_callback=lambda d: d['group__at'],
+        )
+
         # On compte les opérations
         nb_ventes = []
         nb_accounts = []
         nb_liq = []
-        for qs in chunks:
-            nb_ventes.append(
-                tot_ventes(qs))
-            nb_liq.append(
-                tot_ventes(qs.filter(group__on_acc__trigramme='LIQ')))
-            nb_accounts.append(
-                tot_ventes(qs.exclude(group__on_acc__trigramme='LIQ')))
+        for chunk_liq, chunk_no_liq in zip(chunks_liq, chunks_no_liq):
+            sum_accounts = sum(ope['article_nb'] for ope in chunk_no_liq)
+            sum_liq = sum(ope['article_nb'] for ope in chunk_liq)
+            nb_ventes.append(sum_accounts + sum_liq)
+            nb_accounts.append(sum_accounts)
+            nb_liq.append(sum_liq)
+
         context['charts'] = [{"color": "rgb(255, 99, 132)",
                               "label": "Toutes consommations",
                               "values": nb_ventes},