NetFlow Analyzer dumps the data received form the device on to the database based on the timezone set on the server, irrespective of the time of the Device location.
As NetFlow Analyzer dumps the data only based on the server time the time difference between server and router will not affect reporting, but NetFlow Analyzer will display it as a warning in the UI.
To avoid this, you can either change the time on the server to match the Device time or change the time on the device to match in the NetFlow Analyzer server installation time. As time matching happens only based on UTC time, set the time on the device in UTC to match the server to remove the warning message.