Changeing Logs Roll Over

[nking]

I notice that most users use the midnight roll over, I have been thinking of changing my roll over time to 9 am for this reason:

"Daily maximum and minimum temperatures are often taken over
a 24-hour period starting at 9 a.m. local time each day rather than midnight. This
is to avoid dividing each night in half; one very cold night might then contribute
minimum temperatures (one at just before and one after midnight) which would
appear in the record as minima for two successive days."

but, before I do I just thought I would double check that I'm not going to screw up my historical data and, if I decide I want to change it back to midnight, is it likely to cause any major problems.

[steve]

but, before I do I just thought I would double check that I'm not going to screw up my historical data

You'll get inconsistencies. Cumulus stores the data according to your end of day setting, e.g. the dayfile entries are created at the rollover time for the previous 24 hours, so if you change your rollover time, your previous data will now be assumed to represent 0900-0900. Similarly, when you're using an 0900 rollover, the first 9 hours on the first of the month are actually in the previous month's log file, because they 'belong' to that month.

It's not as bad as trying to change your units, which completely invalidates your data, but it makes your previous data "not quite right". As with the units settings, the intention is that Cumulus 2 won't have this issue.

[nking]

Hi Steve,

Thanks for replying, I think I might leave well alone and await Cumulus 2....