diff --git a/CHANGELOG b/CHANGELOG
index 49d2897169..731037c584 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Use TimeDelta field
+
 Version 3.4.0 - 2014-10-20
 * Bug fixes (see mercurial logs for details)
 
diff --git a/view/work_form.xml b/view/work_form.xml
index 8229a965f9..71c76ae904 100644
--- a/view/work_form.xml
+++ b/view/work_form.xml
@@ -21,7 +21,7 @@ this repository contains the full copyright notices and license terms. -->
             <label name="actual_finish_date"/>
             <field name="actual_finish_date"/>
             <label name="duration"/>
-            <field name="duration" widget="float_time" float_time="company_work_time"/>
+            <field name="duration"/>
             <newline/>
             <field name="predecessors" colspan="2"/>
             <field name="successors" colspan="2"/>
diff --git a/work.py b/work.py
index 796c3b0d8f..511b7ffcdb 100644
--- a/work.py
+++ b/work.py
@@ -40,7 +40,9 @@ class Work:
         states={
             'invisible': Eval('type') != 'task',
             }, depends=['type'])
-    duration = fields.Function(fields.Float('Duration'), 'get_function_fields')
+    duration = fields.Function(
+        fields.TimeDelta('Duration', 'company_work_time'),
+        'get_function_fields')
     early_start_time = fields.DateTime("Early Start Time", readonly=True)
     late_start_time = fields.DateTime("Late Start Time", readonly=True)
     early_finish_time = fields.DateTime("Early Finish Time", readonly=True)
@@ -108,12 +110,12 @@ class Work:
                     leafs.add(work.id)
 
                 total_allocation = 0
-                if not work.allocations:
-                    durations[work.id] = (work.effort or 0)
+                if not work.allocations or not work.effort_duration:
+                    durations[work.id] = work.effort_duration
                     continue
                 for allocation in work.allocations:
                     total_allocation += allocation.percentage
-                durations[work.id] = ((work.effort or 0)
+                durations[work.id] = (work.effort_duration
                     / (total_allocation / 100.0))
 
             while leafs:
@@ -168,6 +170,12 @@ class Work:
                         })
                 break
 
+    @property
+    def hours(self):
+        if not self.duration:
+            return 0
+        return self.duration.total_seconds() / 60 / 60
+
     @classmethod
     def add_minutes(cls, company, date, minutes):
         minutes = int(round(minutes))
@@ -290,7 +298,7 @@ class Work:
                     if values[work]['early_start_time']:
                         early_finish_time = self.add_hours(work.company,
                                 values[work]['early_start_time'],
-                                work.duration)
+                                work.hours)
                 values[work]['early_finish_time'] = early_finish_time
 
                 # Propagate constraint_start on successors
@@ -370,7 +378,7 @@ class Work:
                     if values[work]['late_finish_time']:
                         late_start_time = self.add_hours(work.company,
                                 values[work]['late_finish_time'],
-                                -work.duration)
+                                -work.hours)
                 values[work]['late_start_time'] = late_start_time
 
                 # Propagate constraint_finish on predecessors