diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java
index dd5a86db2..dee0d99b1 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java
@@ -808,9 +808,13 @@ public class BaseCalendar extends IntegrationEntity implements ICalendar {
         return calendarDataVersions.get(calendarDataVersions.size() - 1);
     }
 
-    public boolean onlyGivesZeroHours(Days each) {
-        CalendarData last = lastCalendarData();
-        return last.isEmptyFor(each);
+    public boolean onlyGivesZeroHours(Days day) {
+        for (CalendarData each : calendarDataVersions) {
+            if (!each.isEmptyFor(day)) {
+                return false;
+            }
+        }
+        return true;
     }
 
     @Override
@@ -1015,4 +1019,16 @@ public class BaseCalendar extends IntegrationEntity implements ICalendar {
         return lastSequenceCode;
     }
 
+    @AssertTrue(message = "calendars with zero hours are not allowed")
+    public boolean checkConstraintZeroHours() {
+        if ((calendarDataVersions != null) && (!calendarDataVersions.isEmpty())) {
+            for (CalendarData each : calendarDataVersions) {
+                if (!each.isEmpty()) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/CalendarData.java b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/CalendarData.java
index bfb53e588..db690d715 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/CalendarData.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/CalendarData.java
@@ -196,8 +196,15 @@ public class CalendarData extends IntegrationEntity {
     }
 
     boolean isEmptyFor(Days day) {
-        return !isDefault(day) && getCapacityOn(day).isZero() || isDefault(day)
-                && hasParent() && getParent().onlyGivesZeroHours(day);
+        if (isDefault(day)) {
+            if (hasParent()) {
+                return getParent().onlyGivesZeroHours(day);
+            } else {
+                return true;
+            }
+        } else {
+            return getCapacityOn(day).isZero();
+        }
     }
 
     private boolean hasParent() {