Vertical line at 24h before current time

Hi,

I've increased my RRA Archive display from 86400 to 115200 seconds 
(the 'daily' one) so it shows me last 32 hours. 

(e.g. for net traffic displays it can give us perspective of 
how it went 24h before)

I'm looking for a way to insert a line indicating exactly 24h before
the end of graph (or generally : to insert a line at exactly x seconds
before the end of graph).

So that it effectively displays a vertical line showing us exactly the 
last 24 hours.

Problem is, rrdtool expects HH:MM in VRULE value;

How can I make up HH:MM from anything available in the host system?



(cacti Version 0.8.7i)

Kind Regards


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