How to have a X-axis displayed as dates?

I created a X-Y chart, where X are dates. In fact, the X-axis is displayed as a counter : 1 for the firt figure and 2 for the second one, etc.
Thansks in advance for your help

Hello Michel,
You can swap the axis in the Select Data menu:
Insert charts - ONLYOFFICE (Adjust the chart settings)

Hello Carl,
I can not find any date formate in the Display Units dropdown list : only Nothing, Hundreds, Thousands…
[> Please find an exemple spreadsheet. Concerned chart is in top-left corner of tab Ana_coûts.

For info; onlyoffice release and nextcloud 19.](Zaclys cloud)