diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
index 2ef67dfea..e6630a574 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
@@ -75,23 +75,14 @@ public class Task extends TaskElement implements ITaskPositionConstrained {
     @Override
     protected void initializeDates() {
         EffortDuration workHours = EffortDuration.hours(getWorkHours());
-        EffortDuration effortStandardPerDay = EffortDuration.hours(8);
-
-        int daysElapsed = workHours.divideBy(effortStandardPerDay);
-        EffortDuration remainder = workHours.remainderFor(effortStandardPerDay);
+        DurationBetweenDates duration = fromFixedDuration(workHours);
 
         IntraDayDate start = getIntraDayStartDate();
         if (start != null) {
-            IntraDayDate calculatedEnd = IntraDayDate.create(
-                    start.getDate().plusDays(daysElapsed), start
-                            .getEffortDuration().plus(remainder));
-            setIntraDayEndDate(calculatedEnd);
+            setIntraDayEndDate(duration.fromStartToEnd(start));
         } else {
             IntraDayDate end = getIntraDayEndDate();
-            IntraDayDate calculatedStart = IntraDayDate.startOfDay(end
-                    .getDate().minusDays(
-                            daysElapsed + (remainder.isZero() ? 0 : 1)));
-            setIntraDayStartDate(calculatedStart);
+            setIntraDayStartDate(duration.fromEndToStart(end));
         }
     }
 
@@ -573,6 +564,10 @@ public class Task extends TaskElement implements ITaskPositionConstrained {
                 .getDefaultWorkingDay();
     }
 
+    private DurationBetweenDates fromFixedDuration(EffortDuration duration) {
+        return new DurationBetweenDates(0, duration);
+    }
+
     private class DurationBetweenDates {
 
         private final int numberOfWorkableDays;
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java
index a587ed448..6099ab2bd 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java
@@ -505,6 +505,7 @@ public class OrderModel extends IntegrationEntityModel implements IOrderModel {
         Order.checkConstraintOrderUniqueCode(order);
         HoursGroup.checkConstraintHoursGroupUniqueCode(order);
 
+        reattachCalendar();
         reattachCriterions();
         reattachTasksForTasksSources();
 
@@ -594,6 +595,14 @@ public class OrderModel extends IntegrationEntityModel implements IOrderModel {
         }
     }
 
+    private void reattachCalendar() {
+        if (order.getCalendar() == null) {
+            return;
+        }
+        BaseCalendar calendar = order.getCalendar();
+        baseCalendarDAO.reattachUnmodifiedEntity(calendar);
+    }
+
     private void reattachAllTaskSources() {
         // avoid LazyInitializationException for when doing
         // removePredecessorsDayAssignmentsFor