jpgraph: text X scale

Hello

i wanted to draw graph.
On X scale i have time (in seconds). I have measure points for everyday
from 8 AM to 4 PM.
On Y scale i have values.

For one day everything looks fine.
But i wanted to see a graph for two days.
The problem is that bars from the first day are narrowed on the left,
then there is a huge free space (night) and on the right there are bars
from second day.
I wanted to eliminate that free space between (night)
I tried to change X scale from int to text:
$graph->SetScale("textlin");

but it changed anything. Why ? How can i change to text scale to draw data
without caring about XScale ?

Thanx