I have JUST been hunting this issue down, as part of a larger problem (a 1 hour gap in data collection due to DST, which caused several hundred time-based alerts to fire).
Look for a more comprehensive post on this soon, but the upshot is:
- the time inserted into the db is (with 2 or 3 exceptions) using the time of the polling engine that does the inserting
- If you have pollers in two different timezones (we do), you will get data that doesn't match up
- There is no way to make charts, graphs and pages display the timezone being used (if you wanted to set everything to UTC, for example)
Also note that the time on your primary poller MUST be within 5 minutes of your database. And that it doesn't matter at all what time the target devices (ie: nodes) are set to. Which means my staff in China will always see the data from my timezone, not theirs.
Also note that if your poller observes daylight savings, you will have a 1 hour gap in metrics every spring, and a 1 hour overlap in the fall.
The feature request on this is 225282.