FAQ: Difference between revisions

As far as the timestamps in the extreme logs, monthly log, and the graphs, are concerned; Cumulus doesn't do anything in particular for DST. It generates timestamps based on the Windows clock. So basically, at the start of DST (i.e. when the clocks 'go forward') you will get an apparent gap of one hour in your data, and similarly at the end of DST (i.e. when the clocks 'go back') you will get an apparent hour of duplicate timestamps in your logs and graphs. You will tend to get better results if you leave Cumulus running during the clock change, because if it is stopped you may lose data, the exact timing of the affected hours depends on the type of station and when Cumulus was running.

Note that there seems to be an issue with Davis stations, either in the console/logger, or in the Davis DLL which Cumulus uses. If you don't have Cumulus running when DST ends, then when you start Cumulus up again, it doesn't receive all of the logger data it needs to catch up to the present time - the previous hour or so is missing. So with Davis stations, I strongly recommend that you leave Cumulus running at the end of DST, if at all possible.

For Fine Offset stations if you don't have Cumulus running when DST ends, then when you start Cumulus up again, the catch up misses off the first hour after the time Cumulus was stopped.  This is because the console memory does not time-stamp the data blocks and Cumulus does not remember the console data block used just before shutdown, after all depending on how long Cumulus has been stopped and the station logging interval, the old memory location could be overwritten by now. On restart it just tries to read the appropriate number of hours worth of observations back from the block now marked as latest.  If it was stopped at 2200 DST and restarted at 0600 standard time, Cumulus catches up with the last 8 hours worth of stored measurements as if going back to 2200 standard time, that means it stops at 2300 DST. At the start of DST, the catch up will duplicate the last hour that Cumulus was previously operating. (Stopping from 2200 standard time to 0600 DST the catch up goes back to 2200 DST or 2100 standard time).