# [rrd-users] Re: RRD setup when collection only daily

Serge Maandag serge.maandag at staff.zeelandnet.nl
Mon Apr 22 14:36:06 MEST 2002

```Thanx,

I see the difference now.
The first entry will always start at an epoch time that's divisible by
the stepsize.
I thought it would start at the time of the first update.

Taking 3600 as the stepsize is logical since the localtimes change with
1 hour steps.
You were right about the xff remark too, I've learned today :)

Serge.

-----Original Message-----
From: Alex van den Bogaerdt [mailto:alex at ergens.op.HET.NET]
Sent: Friday, April 19, 2002 11:23 PM
To: Serge Maandag
Cc: RRD users
Subject: Re: [rrd-users] Re: RRD setup when collection only daily

Serge Maandag wrote:

> If he sets his step to 86400 and his ds heartbeat to:
> 86400 + (a small interval in case he runs late with his daily update)
> And he does his first update at midnight, wouldn't that just be what
> he wants? His pdp's would be at 00:00 exactly.

No, unless you work in UTC time.  All times inside RRDtool are a whole
multiple of the step size.  If the step size is 86400, today would be
1019174400.  This is 1019250638 - (1019250638 % 86400). Perl shows the
time: perl -e 'use POSIX;print ctime(1019174400)' which results in 'Fri
Apr 19 02:00:00 2002' (local time).

> I can see why your method works, but wonder what the advantage is.

If the step size is 3600, the current time minus the modulo would be
perl -e 'use POSIX;print ctime(1019250638 - (1019250638 % 3600));' Fri
Apr 19 23:00:00 2002

So, if I would update now, in the first example I would update at 02:00
local time, in the second example I would update at 23:00 local time.
Similarly, if I would update just after midnight I would still update at
02:00 (the day before!) in the first example while I would update at
00:00 (*that* day) in the second example.

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