+This gets replaced by a strftime-formatted time using the format
+I<strftime-format> on either I<start-spec> or I<end-spec> depending on
+whether I<START> or I<END> is specified. Both I<start-spec> and I<end-spec>
+must be supplied as either could be relative to the other. This is intended
+to allow pretty titles on graphs with times that are easier for non RRDtool
+folks to figure out than "-2weeks".
+
+Note that again, if you return : (colon) from your strftime format,
+you may have to escape them using \ if the time is to be used as an
+argument to a GRAPH command.