Updated README with datetime format

README.md

@@ -33,7 +33,13 @@ application:
 
 # Data from systems to datapoints
 
-`curl -d "$(time +'%F %T +02')" http://localhost:9000/entry/datapoint_name`
+`curl -d 200 http://localhost:9000/entry/datapoint_name`
+
+## Datetime format
+
+Datetime data is to be in the format of "2006-01-02T15:04:05+02:00" or "2006-01-02T15:04:05+0200".
+
+Use `date '+%FT%T%z'` to get a value from systems in correct format.
 
 # Theming