diff --git a/src/BreCalClient/EditTimesAgencyIncomingControl.xaml.cs b/src/BreCalClient/EditTimesAgencyIncomingControl.xaml.cs
index b1eba3b..e259adf 100644
--- a/src/BreCalClient/EditTimesAgencyIncomingControl.xaml.cs
+++ b/src/BreCalClient/EditTimesAgencyIncomingControl.xaml.cs
@@ -133,6 +133,12 @@ namespace BreCalClient
                 return false;
             }
 
+            if((this.datePickerTidalWindowFrom.Value.HasValue && !this.datePickerTidalWindowTo.Value.HasValue) || (!this.datePickerTidalWindowFrom.Value.HasValue && this.datePickerTidalWindowTo.Value.HasValue))
+            {
+                message = BreCalClient.Resources.Resources.textTidalBothValues;
+                return false;
+            }
+
             return true;
         }
 
diff --git a/src/BreCalClient/EditTimesAgencyOutgoingControl.xaml.cs b/src/BreCalClient/EditTimesAgencyOutgoingControl.xaml.cs
index 7258006..615236a 100644
--- a/src/BreCalClient/EditTimesAgencyOutgoingControl.xaml.cs
+++ b/src/BreCalClient/EditTimesAgencyOutgoingControl.xaml.cs
@@ -143,6 +143,12 @@ namespace BreCalClient
                 return false;
             }
 
+            if ((this.datePickerTidalWindowFrom.Value.HasValue && !this.datePickerTidalWindowTo.Value.HasValue) || (!this.datePickerTidalWindowFrom.Value.HasValue && this.datePickerTidalWindowTo.Value.HasValue))
+            {
+                message = BreCalClient.Resources.Resources.textTidalBothValues;
+                return false;
+            }
+
             return true;
         }
 
diff --git a/src/BreCalClient/EditTimesAgencyShiftingControl.xaml.cs b/src/BreCalClient/EditTimesAgencyShiftingControl.xaml.cs
index e8398ce..aa34817 100644
--- a/src/BreCalClient/EditTimesAgencyShiftingControl.xaml.cs
+++ b/src/BreCalClient/EditTimesAgencyShiftingControl.xaml.cs
@@ -151,6 +151,12 @@ namespace BreCalClient
                 return false;
             }
 
+            if ((this.datePickerTidalWindowFrom.Value.HasValue && !this.datePickerTidalWindowTo.Value.HasValue) || (!this.datePickerTidalWindowFrom.Value.HasValue && this.datePickerTidalWindowTo.Value.HasValue))
+            {
+                message = BreCalClient.Resources.Resources.textTidalBothValues;
+                return false;
+            }
+
             return true;
         }
 
diff --git a/src/BreCalClient/Resources/Resources.Designer.cs b/src/BreCalClient/Resources/Resources.Designer.cs
index aeada56..2cc1e8c 100644
--- a/src/BreCalClient/Resources/Resources.Designer.cs
+++ b/src/BreCalClient/Resources/Resources.Designer.cs
@@ -1208,6 +1208,15 @@ namespace BreCalClient.Resources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to For a tidal window both values must be set.
+        /// </summary>
+        public static string textTidalBothValues {
+            get {
+                return ResourceManager.GetString("textTidalBothValues", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Tidal window.
         /// </summary>
diff --git a/src/BreCalClient/Resources/Resources.de.resx b/src/BreCalClient/Resources/Resources.de.resx
index 18947eb..cdd4e08 100644
--- a/src/BreCalClient/Resources/Resources.de.resx
+++ b/src/BreCalClient/Resources/Resources.de.resx
@@ -541,4 +541,7 @@
   <data name="textZoneEntryInThePast" xml:space="preserve">
     <value>Zeit Reviereintritt liegt in der Vergangenheit</value>
   </data>
+  <data name="textTidalBothValues" xml:space="preserve">
+    <value>Für das Tidenfenster müssen beide Zeiten angegeben werden</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/BreCalClient/Resources/Resources.resx b/src/BreCalClient/Resources/Resources.resx
index 14cf0f9..28af8fe 100644
--- a/src/BreCalClient/Resources/Resources.resx
+++ b/src/BreCalClient/Resources/Resources.resx
@@ -487,6 +487,9 @@
   <data name="textTerminal" xml:space="preserve">
     <value>Terminal</value>
   </data>
+  <data name="textTidalBothValues" xml:space="preserve">
+    <value>For a tidal window both values must be set</value>
+  </data>
   <data name="textTidalWindow" xml:space="preserve">
     <value>Tidal window</value>
   </data>