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 QCChart2D and QCChart2D CF (VB and C#)
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Posted - 27 Jul 2017 :  17:14:28  Show Profile  Reply with Quote
I'm very interested on your input regarding how to plot across Daylight Saving Time (DST)fall back and spring forward. It is my understanding this is not directly supported in QCRTGraph...

How we here at ICU Medical were hoping to handle this was to plot all data in UTC, then override the X time axis label (TimeAxisLabels.cs) as follows.

1. Convert the axis labeling only from UTC to local time
2. In the spring DST change (clock jumps from 2am to 3am), we'd just insert a break at 2am.
3. In the fall DST change (clock jumps from 2am to 1am), we'd just override the x axis labeling so it reads 12am, 1am, 1am, 2am, 3am...

However, in order to accomplish #'s 1 and 3 above, I'm having trouble identifying precisely how/where to override the axis labeling.

Please Advise.

Karl Miller

ICU Medical


1569 Posts

Posted - 27 Jul 2017 :  18:06:19  Show Profile  Reply with Quote
Sorry but we have no idea on how to accomplish what you describe. It has never come up before so we have never considered how to do it. I don't think disconnecting the time-axis labels (local time) from the current coordinate system (UTC time) is workable across all aspects of the software.

You can just do everything in UTC time, in which case the point is moot. Or you can convert to local time. In that case you would scale everything for local time. In the Spring DST change you would just let any plotted data jump over the 2AM to 3AM time period. You can place a ChartText label on the chart to mark the 2AM to 3AM as an invalid time period because of DST. In the case of the Fall DST change (2AM to 1AM0, you would still plot the data as is. Since your data might contain duplicate x-data values for the time period 1AM to 2AM, the plotted would back track from 2AM back to 1AM and continue the trace from 1AM forward. The plot would show a double line from 1AM to 2AM, which would be perfectly valid for data in local time. I don't think getting it beyond this is worth the effort. But if it an absolute requirement in your application, you can write a specification on exactly what you want it to look like. We can quote you on what it would cost to add some sort of flag to the software which would process the time-axis labels, and data values, to your requirement.
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