[rrd-users] Please help me understand this

[Marklar Inc.]

On Oct 15, 2010, at 12:02 AM, Simon Hobson wrote:

> Marklar Inc. wrote:
>> I really need help understanding this. Im trying to graph five 
>> values from 04-10-10 - 08-10-10 which is from Monday to Friday.
>> 
>> When i do a rrdtool dump, is see the values are correct inserted 
>> from Monday to Friday. But when i graph it, it shows from Sunday to 
>> Thursday.
>> One day to early. Im propably doing something wrong.
>> 
>> The commands are listed below.
>> 
>> Thanks.
>> 
>> rrdtool create AAPL.rrd --step 86400 --start 1286107200 
>> DS:open:GAUGE:86400:0:100000  RRA:LAST:0.5:1:1825
>> rrdtool update AAPL.rrd 1286193600:281.60
>> rrdtool update AAPL.rrd 1286280000:282.00
>> rrdtool update AAPL.rrd 1286366400:289.59
>> rrdtool update AAPL.rrd 1286452800:290.34
>> rrdtool update AAPL.rrd 1286539200:291.71
>> rrdtool graph AAPL.png --start 1286020800 --end  1286576091 --width 
>> 1600 --watermark "this is wierd" DEF:open=AAPL.rrd:open:LAST 
>> LINE1:open#000000
> 
> 1286576091 is about half past ten in the evening - so the day is not 
> complete and cannot be plotted as a value. The latest whole step 
> period ended at midnight (UTC) almost a day earlier.
> 
> It's really, really a good idea to use start and end times which 
> exactly match the boundaries of the stored data buckets. Also note 
> that all times are relative to UTC, so if your timezone is +1, your 
> one day periods run from 1am to 1am local time.
> 
> -- 
> Simon Hobson

I dont really understand the answer. What is the explaination that the graph plots its first value on sunday, when the dump clearly says that it is monday?