diff --git a/simulation/src/de/c3ma/ollo/LuaSimulation.java b/simulation/src/de/c3ma/ollo/LuaSimulation.java
index 35d7fb0..5d3023d 100644
--- a/simulation/src/de/c3ma/ollo/LuaSimulation.java
+++ b/simulation/src/de/c3ma/ollo/LuaSimulation.java
@@ -10,4 +10,6 @@ package de.c3ma.ollo;
 public interface LuaSimulation {
 
     public void rebootTriggered();
+
+    public void setSimulationTime(long timeInMillis);    
 }
diff --git a/simulation/src/de/c3ma/ollo/WS2812Simulation.java b/simulation/src/de/c3ma/ollo/WS2812Simulation.java
index 148e20f..08b80a2 100644
--- a/simulation/src/de/c3ma/ollo/WS2812Simulation.java
+++ b/simulation/src/de/c3ma/ollo/WS2812Simulation.java
@@ -165,4 +165,9 @@ public class WS2812Simulation implements LuaSimulation {
 			throw new RuntimeException("Copy into temporary folder failed; script not available");
 		}
 	}
+
+    @Override
+    public void setSimulationTime(long timeInMillis) {
+        ESP8266Time.setOverwrittenTime(timeInMillis);
+    }
 }
diff --git a/simulation/src/de/c3ma/ollo/mockup/ESP8266Time.java b/simulation/src/de/c3ma/ollo/mockup/ESP8266Time.java
index 16e442c..a8f48df 100644
--- a/simulation/src/de/c3ma/ollo/mockup/ESP8266Time.java
+++ b/simulation/src/de/c3ma/ollo/mockup/ESP8266Time.java
@@ -23,6 +23,8 @@ public class ESP8266Time extends TwoArgFunction {
     
     private static long gSimulationStartTime = 0;
     
+    private static long gOverwrittenTime = 0;
+    
     @Override
     public LuaValue call(LuaValue modname, LuaValue env) {
         env.checkglobals();
@@ -48,11 +50,16 @@ public class ESP8266Time extends TwoArgFunction {
             gSimulationStartTime = System.currentTimeMillis();
         }
         
-        long time = System.currentTimeMillis();
-        if (ESP8266Tmr.gTimingFactor > 1) {
-            time = gSimulationStartTime + ((time - gSimulationStartTime) * ESP8266Tmr.gTimingFactor);
+        if (gOverwrittenTime == 0) {
+            /* Time simulation is disabled -> calculate something according to the speedup factor */
+            long time = System.currentTimeMillis();
+            if (ESP8266Tmr.gTimingFactor > 1) {
+                time = gSimulationStartTime + ((time - gSimulationStartTime) * ESP8266Tmr.gTimingFactor);
+            }
+            return time;
+        } else {
+            return gOverwrittenTime;
         }
-        return time;
     }
 
     private class SyncFunction extends ThreeArgFunction {
@@ -87,5 +94,9 @@ public class ESP8266Time extends TwoArgFunction {
         }
         
     }
+
+    public static void setOverwrittenTime(long timeInMillis) {
+        gOverwrittenTime = timeInMillis;
+    }
     
 }
diff --git a/simulation/src/de/c3ma/ollo/mockup/ui/WS2812Layout.java b/simulation/src/de/c3ma/ollo/mockup/ui/WS2812Layout.java
index 2200d60..a68c4b9 100644
--- a/simulation/src/de/c3ma/ollo/mockup/ui/WS2812Layout.java
+++ b/simulation/src/de/c3ma/ollo/mockup/ui/WS2812Layout.java
@@ -2,7 +2,6 @@ package de.c3ma.ollo.mockup.ui;
 
 import java.awt.BorderLayout;
 import java.awt.Color;
-import java.awt.Event;
 import java.awt.Font;
 import java.awt.GridLayout;
 import java.awt.event.ActionEvent;
@@ -11,8 +10,8 @@ import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.IOException;
-import java.time.LocalDate;
 import java.util.ArrayList;
+import java.util.GregorianCalendar;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -26,7 +25,6 @@ import javax.swing.event.DocumentEvent;
 import javax.swing.event.DocumentListener;
 
 import de.c3ma.ollo.LuaSimulation;
-import javafx.scene.control.DatePicker;
 
 /**
  * created at 02.01.2018 - 12:57:02<br />
@@ -124,7 +122,13 @@ public class WS2812Layout extends JFrame {
 		         final String pattern = "(\\d{4})-(\\d{2})-(\\d{2}) (\\d{2}):(\\d{2}):(\\d{2})";
 		         final String current = dateTime.getText();
 		        
-		         
+		         if (current.length() <=0) {
+		             /* color "nothing" green */
+		             dateTime.setForeground(Color.GREEN);
+		             /* disable the time simulation */
+		             nodemcuSimu.setSimulationTime(0);
+		             return;
+		         }
 		         
 		         if (!current.matches(pattern)) {
 		             dateTime.setForeground(Color.RED);
@@ -161,7 +165,10 @@ public class WS2812Layout extends JFrame {
                              break;
 		                 }	
 		             }
-		             System.out.println("Set time to: " + year + "-" + month + "-" + day + " " + hour + ":" + minute + ":" + second);
+		             System.out.println("[GUI] Set time to: " + year + "-" + month + "-" + day + " " + hour + ":" + minute + ":" + second);
+		             GregorianCalendar gc = new GregorianCalendar(year, month, day, hour, minute, second);
+		             
+		             nodemcuSimu.setSimulationTime(gc.getTimeInMillis());
 		         }
 		      }
 		    });