I had problems with the date labels in the x-axis on a small number of observations and a chart width of 800 and less:
I have, in theory, x-axis (BottomAxis) ranges from 0 to an indefinite number of days/hours.
In praxis one day 0 to 24, two days 0-48 so on.
Depending on the time of observation on a day:
At time 00:00, no observation, 01:00 one observation, so on.
The width of the Chart is default 800 but sizeable.
This setting seems to work well on smaller or wider forms:
-BottomAxis, Marks.Style = smsLabel.
-TDateTimeChartSource add to the Chart, BottomAxis.
In the TDateTimeChartSource:
DateTimeIntervalChartSource1.Params.MaxLength := 60; (may be up to 70 but less than 80 )
DateTimeIntervalChartSource1.Params.MinLength := 10; (seems to be best)
DateTimeIntervalChartSource1.Params.Tolerance := 5; (or less)
DateTimeIntervalChartSource1.Params.NiceSteps := '1|2|4|6|12';
The NiceSteps did the trick on small numbers.
This may be set in FormCreate or Object inspector.
Hope this help others