diff --git a/dv-task-manager.py b/dv-task-manager.py
index ae6bf11..9e5b40a 100755
--- a/dv-task-manager.py
+++ b/dv-task-manager.py
@@ -6,67 +6,48 @@ import calendar
 
 from yaml import load
 from icalendar.parser import Contentlines, Contentline
+from dateutil.rrule import rrule, FREQNAMES
 import caldav
 
+
 class Task:
     def __init__(self, ref_date, name, data):
         self.ref_date = ref_date
         self.name = name
-        only = data['only'].split(',') if 'only' in data else None
-        if data['periodicity'] == 'monthly':
-            self.date_begin = self.parse_date_monthly(data['date-begin'], only)
-            self.date_end = self.parse_date_monthly(data['date-end'], only)
-        elif data['periodicity'] == 'weekly':
-            pass
-
+        data['start']['freq'] = FREQNAMES.index(data['start']['freq'])
+        self.date_begin = rrule(count=1, dtstart=ref_date, **data['start'])[0]
+        self.date_end = self.date_begin + datetime.timedelta(microseconds=-1, **data['duration'])
 
         self.title = data['title']
-        self.body  = data['body']
+        self.body = data['body']
         self.priority = data['priority']
 
-    def parse_date_monthly(self, day, only=None):
-        if day < 0:
-            last_day_month = calendar.monthrange(self.ref_date.year, self.ref_date.month)[1]
-            day = last_day_month + day + 1
-
-        if only is not None:
-            only.sort()
-            for selected in only:
-                if int(selected) >= self.ref_date.month:
-                    month = int(selected)
-                    break
-            if month is None:
-                month = only[0]
-        else:
-            month = self.ref_date.month
-
-        return datetime.date(year=self.ref_date.year, month=month, day=day)
-
     def to_ical(self):
         current_dtstamp = datetime.datetime.now().strftime('%Y%m%dT%H%M%SZ')
         uid = "DV-Taskmanager-%s-%s" % (self.name, self.date_end.strftime('%Y%m%d'))
         c = Contentlines([
-          Contentline('BEGIN:VCALENDAR'),
-          Contentline('VERSION:2.0'),
-          Contentline('PRODID:-//Example Corp.//CalDAV Client//EN'),
-          Contentline('BEGIN:VTODO'),
-          Contentline('DTSTAMP:%s' % current_dtstamp),
-          Contentline('CREATED:%s' % current_dtstamp),
-          Contentline('UID:%s' % uid),
-          Contentline('SEQUENCE:%s' % '4'),
-          Contentline('LAST-MODIFIED:%s' % current_dtstamp),
-          Contentline('DESCRIPTION:%s' % self.body),
-          Contentline('SUMMARY:%s' % self.title),
-          Contentline('PRIORITY:%s' % 1),
-          Contentline('DUE;VALUE=DATE:%s' % self.date_end.strftime('%Y%m%d')),
-          Contentline('DTSTART;VALUE=DATE:%s' % self.date_begin.strftime('%Y%m%d')),
-          Contentline('PERCENT-COMPLETE:0'),
-          Contentline('END:VTODO'),
-          Contentline('END:VCALENDAR')
+            Contentline('BEGIN:VCALENDAR'),
+            Contentline('VERSION:2.0'),
+            Contentline('PRODID:-//Example Corp.//CalDAV Client//EN'),
+            Contentline('BEGIN:VTODO'),
+            Contentline('DTSTAMP:%s' % current_dtstamp),
+            Contentline('CREATED:%s' % current_dtstamp),
+            Contentline('UID:%s' % uid),
+            Contentline('SEQUENCE:%s' % '4'),
+            Contentline('LAST-MODIFIED:%s' % current_dtstamp),
+            Contentline('DESCRIPTION:%s' % self.body),
+            Contentline('SUMMARY:%s' % self.title),
+            Contentline('PRIORITY:%s' % 1),
+            Contentline('DUE;VALUE=DATE:%s' % self.date_end.strftime('%Y%m%d')),
+            Contentline('DTSTART;VALUE=DATE:%s' % self.date_begin.strftime('%Y%m%d')),
+            Contentline('PERCENT-COMPLETE:0'),
+            Contentline('END:VTODO'),
+            Contentline('END:VCALENDAR')
         ])
 
         return c.to_ical()
 
+
 class Client:
     def __init__(self, url):
         self.client = caldav.DAVClient(url)
@@ -76,19 +57,19 @@ class Client:
     def add_event(self, event):
         self.calendar.add_event(task.to_ical())
 
-#conf = load('./configuration.yml')
 
-ref_date = datetime.date.today() + datetime.timedelta(days=3)
+# conf = load('./configuration.yml')
+
+ref_date = datetime.date.today() + datetime.timedelta(days=-3)
 with open('./tasks.yml', 'r') as content_file:
     tasks_conf = load(content_file.read())
 
 task_list = []
 for task_name, task_data in tasks_conf.items():
-    t = Task(ref_date, task_name, task_data);
-    if (t.date_begin == ref_date):
+    t = Task(ref_date, task_name, task_data)
+    if t.date_begin.date() == ref_date:
         task_list.append(t)
 
-import ipdb; ipdb.set_trace()
 url = "https://ggentile:ID0t'8h6@cloud.dorfsvald.net/webdav/ggentile/calendar.ics/"
 client = Client(url)
 for task in task_list:
diff --git a/tasks.yml b/tasks.yml
index 58aed6e..9418a25 100644
--- a/tasks.yml
+++ b/tasks.yml
@@ -1,38 +1,52 @@
-#see http://dateutil.readthedocs.io/en/stable/rrule.html
+# see http://dateutil.readthedocs.io/en/stable/rrule.html
+# freq, dtstart=None, interval=1, wkst=None, count=None, until=None, bysetpos=None,
+# bymonth=None, bymonthday=None, byyearday=None, byeaster=None, byweekno=None, byweekday=None,
+# byhour=None, byminute=None, bysecond=None, cache=False
+# Where freq must be one of YEARLY, MONTHLY, WEEKLY, DAILY, HOURLY, MINUTELY, or SECONDLY.
 
 reglement_piano:
-  periodicity: monthly
-  date-begin: -4
-  date-end: -1
+  start:
+    freq: MONTHLY
+    bymonthday: -5
+  duration:
+    days: 5
   title: Règlement Piano
   body: 578236
   priority: 1
 loyer:
-  periodicity: monthly
-  date-begin: 1
-  date-end: 10
+  start:
+    freq: MONTHLY
+    bymonthday: 1
+  duration:
+    days: 10
   title: Loyer
   body: https://fr.foncia.com/login\nA797GEA4EP23F
   priority: 1
 declaration_polemploi:
-  periodicity: monthly
-  date-begin: 1
-  date-end: 10
+  start:
+    freq: MONTHLY
+    bymonthday: 1
+  duration:
+    days: 10
   title: Déclaration Pôle Emploi
   body: N/A
   priority: 1
 declaration_ae:
-  periodicity: monthly
-  only: 1,4,7,10
-  date-begin: 1
-  date-end: 10
+  start:
+    freq: MONTHLY
+    bymonthday: 1
+    bymonth: [1,4,7,10]
+  duration:
+    days: 30
   title: Déclaration AE
   body: N/A
   priority: 1
 facturation_x2i:
-  periodicity: monthly
-  date-begin: -4
-  date-end: -1
+  start:
+    freq: MONTHLY
+    bymonthday: -4
+  duration:
+    days: 4
   title: Facture X2I
   body: N/A
   priority: 1