If you do a rrdtool graph -s -3600 .... then the generated graph is a graph of the last 3600 seconds (1h). How is the 1h calculated? Is this based on the current time (within the current time zone) or is this based on the current time (but seen in UTC) or is this the last 1h that was logged within the RRD file? Dirk Bulinckx.