Maybe this has been clarified somewhere else (I looked at the daylight savings time threads), but couldn’t find anything. Today I was running some tests on some code that stored historical data on the hour, so rather than waiting an hour each time, I would just set the clock back to something like 8:58. But each time I did that, the timer that was triggering my historizer stopped incrementing (“running” was still true) and the table that was displaying the historiccal data stopped updating (I had it set to relative). Obviously now that I know what’s going on, I just set the time off and on again to get it going, and open and close the table data binding to get it to refresh, but what is going to happen this fall? Do I need to programatically nudge everything when I see the time go backwards? Or is this a bug? It doesn’t seem quite right.
Setting the clock forwards and backwards is not a good idea with Ignition. A lot of Ignition is dependent on the clock, such as scan classes, timers, etc. Setting the clock backwards and forwards may cause these parts to stop working, in which case you would have to restart Ignition. You should programmatically nudge the data backwards and forwards instead.
I don’t believe that DST will be a problem, because when you just change the clock on the computer you’re completely bypassing all of the “intelligence” built into the various calendar systems. That said, we’ll certainly look into it again, because proper handling of DST is a tricky but important subject.