This is just a heads up in case someone else finds the same issue. We have a number of raspberry pis displaying timeseries data on a lan. One of the nodes was displaying old data and I couldn’t figure out what was going on. I spent quite some time diagnosing the problem when I suddenly realised that Grafana displays data based on the client time and not the server time. For me this was a truely bizarre discovery. I’ve never seen a web page which used the viewing workstations time.
Anyway, if you are using devices for displaying grafana data, make sure your ntp config is working!