diff --git a/README.md b/README.md
index c47e8ba..9615571 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,8 @@ your InfluxDb.
 
 # How does it work
 
-* get the relevant CSVs from https://www.madavi.de/sensor/csvfiles.php
+* get the relevant CSVs from https://www.madavi.de/sensor/csvfiles.php (dates
+  are in UTC!)
 * delete all lines that you already have in your DB (keep the header)
 * export settings as environment vars in case they differ from the defaults
   (INFLUXDB_HOST, INFLUXDB_PORT, INFLUXDB_DATABASE, SENSOR_ID)