fix datetime

mqtt_publish_temp.py

@@ -1,5 +1,5 @@
 import time
-import datetime
+from datetime import datetime
 import subprocess
 import sys
 
@@ -14,7 +14,7 @@ import paho.mqtt.client as paho
 now = datetime.now()
 #print("now =", now)
 #Output format: DD/MM/YYYY H:M:S
-dt_string = now.strftime("%d/%m/%Y %H:%M:%S")
+dt_string = now.strftime("%d-%m-%Y %H:%M:%S")
 
 # MQTT credentials
 #mqtt_username  = 'homeassistant' # MQTT client username