diff --git a/WLAN_Thermometer.ino b/WLAN_Thermometer.ino
index 3533b02..e231ecc 100644
--- a/WLAN_Thermometer.ino
+++ b/WLAN_Thermometer.ino
@@ -24,6 +24,7 @@
 #define KRATE_TEMP            5000
 #define KRATE_TIME            500
 #define KRATE_RESET_AP_DATA   5000
+#define KRATE_CHECK_DATETIME  250000
 #define ONBOARD_LED           2
 #define NTP_TIMEOUT           15000
 #define WIFI_CONNECT_TIMEOUT  30
@@ -157,6 +158,7 @@ void setup()
   sched.addJob(show_temperature, KRATE_TEMP);
   sched.addJob(show_time, KRATE_TIME);
   sched.addJob(check_reset_ap_data, KRATE_RESET_AP_DATA);
+  sched.addJob(check_datetime, KRATE_CHECK_DATETIME);
 
   get_sensor_data();
   temp[MIN] = temp[ACT];
@@ -377,7 +379,6 @@ void show_time(void)
   {
     strcpy(date_string, "--:--:----");
     strcpy(time_string, "--:--:--");
-    DateTime.forceUpdate();
   }
 
   if (strcmp(date_string, date_string_old))
@@ -576,3 +577,14 @@ void ap_data_reset(void)
   delay(1000);
   ESP.restart();
 }
+
+void check_datetime(void)
+{
+  if (!DateTime.isTimeValid())
+  {
+    lcd.setCursor(0, 0);
+    lcd.print("  Time update   ");
+    DateTime.forceUpdate();
+    show_time();
+  }
+}