Unable to adjust X-axis labels and tick marks (timestamp) in a Calc line chart


I’m charting date & time based data in a line chart (e.g. 1-minute samples over a 24 hr or 48 hr period, = 1,440 samples/24 hr). The X-axis displays date and time. The X-axis labels that are displayed are set automatically. I can’t adjust the start of the labelling (it now displays a start time of 16:02, where it should be 16:00), and the interval is set automatically (e.g. 27 minutes) and can’t be adjusted. I would like to format the axis to start with the 1st sample as label, and manually set the interval of both the labels and the tick marks. I formatted the X-axis timestamp both as text (=text(REF),MM-DD-YYYY) and as number. It doesn’t produce a different result.