Fixes.

WLAN_Thermometer.ino

@@ -34,9 +34,9 @@
 
 LiquidCrystal_I2C lcd(LCD_I2C_ADDR, LCD_COL, LCD_ROW);
 looper sched;
-float temp[3];
-float hum[3];
-float heat[3];
+float temp[3] = { NAN, NAN, NAN };
+float hum[3] = { NAN, NAN, NAN };
+float heat[3] = { NAN, NAN, NAN };
 bool led_state;
 String header;
 WiFiServer server(80);
@@ -377,6 +377,7 @@ void show_time(void)
   {
     strcpy(date_string, "--:--:----");
     strcpy(time_string, "--:--:--");
+    DateTime.forceUpdate();
   }
 
   if (strcmp(date_string, date_string_old))
@@ -491,10 +492,10 @@ void get_sensor_data(void)
     heat[ACT] = NAN;
 
   if (minmax_enabled == false && millis() > FIRST_MIN_MAX)
-  {
-    if (!isnan(temp[ACT]) && !isnan(hum[ACT]) && !isnan(heat[ACT]))
-      minmax_enabled = true;
+    minmax_enabled = true;
 
+  if (minmax_enabled == false)
+  {
     if (!isnan(temp[ACT]))
     {
       temp[MIN] = temp[ACT];
@@ -513,8 +514,7 @@ void get_sensor_data(void)
       heat[MIN] = heat[ACT];
     }
   }
-
-  if (minmax_enabled == true)
+  else
   {
     if (!isnan(temp[ACT]))
     {