[rrd-users] rrd starting at a certain date

[Stefan M. Brandl]

On Tue, Apr 13, 2010 at 10:19:32AM +0100, Simon Hobson wrote:
> Stefan M. Brandl wrote:
> 
> >  > Timezone ?
> >>
> >
> >Seems not to be the problem.
> >If I set the start-date 3600 seconds higher or 3600 seconds lower,
> >the result is always the same. Startdate is always set to 1267056000 (look
> >in the resulting rrd-dump).
> >
> >>  Your email says +2 (European summer time ?), so midnight by your
> >>  clock is 22:00 UTC. RRCTool only uses UTC.
> >>
> >>  In any case, the start time in an RRD file is largely irrelevant.
> >
> >Why?
> >I want a 1 week interval with data inserted every friday.
> 
> I'd missed the step size of 604800.
> 
> Because that's the way it works<period>. Every step starts on an 
> integer multiple of step size since unix epoch. It's a design 
> decision to work only in UTC which avoids the significant 
> complications of working in a local (and changeable) timezones. I 
> suppose it would be possible to add support for a fixed offset from 
> Unix epoch - but I'm sure if that were added, it wouldn't be long 
> before people started asking to be able to change it.
> 
> 1267142400 misses that and so RRDtool rounds it until it does fit.
> 

Ok, now I understand.
Thanks for the detailed explanation.


Stefan