There is no "elapsed time" scale; time scales must be initialized with valid date/time record.
You cannot use a start time of January 1, 1 AD, which would coorespond to a start time of 0.
But all you are interested in representation of an elapsed time scale. So just start your time scale with todays date (or any date really), initial time - 0:00:00. And end you time scale with todays date, some other time - 3:30:00. Use a TimeAxisLabels time label format that does not show the date, only the time. See the example program ScatterPlots.ScatterPoints.
ChartCalendar currentDate = new ChartCalendar();
ChartCalendar.SetTOD(currentDate,0,0,0);
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TimeAxisLabels xAxisLab = new TimeAxisLabels(xAxis);
// Get rid of the initial date crossover label under the 0:00:00
xAxisLab.DateCrossoverMode = ChartObj.NO_DATECROSSOVER;
xAxisLab.AxisLabelsFormat = ChartObj.TIMEDATEFORMAT_24HMS;
If you start with a time scale in the 0:00:00 - XX:XX:XX range you must make sure that the time stamp on the data you use to update the real-time variable represents the proper time. Use the overlaod of SetCurrentValue that uses an explicit time stamp.
ChartCalendar tod = new ChartCalendar(); // get current time
// Increment elapsed time 10 seconds for each update.
ChartCalendar.SetTODSeconds(currentDate, 10 * updateCounter);
currentTemperature1.SetCurrentValue(tod, currentTemperatureValue1);
updateCounter++;
