Strange differences on graphs data when changing period

[phphil]

When I watch graphs there is something that really confuse me. In example, analyzing the "CPU utilization" graph (Template Module Linux CPU by Zabbix agent), if I select the last 7 days period, I can see the following data:


It seems a quiet situation, the CPU is really not stressed, that's good I can add more load since the CPU usage is never greater than 30-35% circa.



But if I select a different period of time, lets say the last 2 days, I see a completely different scenario:



The CPU usage reach the 75% on 08-10 (10th August) at 03:00 AM, and this data does not match the data returned by the previous graph in the same datetime, and anyway in any point. How is this possible, there is maybe a setting that I can tweak in order to fix this?


But there is more... if I really look closely in the detail, in the last 7 days graph I can see that the max value, the peak, happened on 08-09 (9th August) at 03:00 AM, Instead in the last 2 days graph it seems the opposite, the max value is reached on 08-10 (10th August) at 03:00 AM.

My main concern is the first issue, can I do something about it? If there is some minor incorrectness like the one I just described, I can leave with that.

Thanks a lot for any help

[cyber]

One thing is, that in case of longer period, there is not enough pixels on screen to draw data point for each value. In such case trend data is displayed, even if history data may be present...

https://www.zabbix.com/documentation/current/manual/config/visualization/graphs/simple#generating_f

...