Hi Clo,
Thanks for using Syncfusion products.
If your intention is to set different date time interval to chart axis based on data points value(first and last value), we suggest you to calculate the hour between start and end time of data point and then set appropriate interval type to date time range. Please find the attached sample for this query.
Please let us know if we misunderstood your query please provide us some clear details and screenshots about this issue otherwise try to reproducing the issue in the above sample and send us the modified sample, so that we could sort out the cause of the issue and provide you a solution.
Regards,
Vijayabharathi
Sample_XDateTime_1404cad4.zip