Create historical data

Hi all experts!

I have a couple of gauges in my system that is sending data to xymon.

 
That is fine. It is plotting nicely on graphs for the day, 2 days, 48 days
and two years.

 
But It only plots data from a certain date (the start date)

 
I would like to dig up the data from our database and re-create the
historical data.

 
How can that be done ?

 
Any tips or ideas ?!

 
I assume I need to use some lowlevel formatting with the rrd tool – but how
?

 
I just need some tips&trix so I can recreate two values for a specific date
into rrd database.

 
Anyone knows ?

 
//Björn