Date read as text in report linked to sharepoint

Hi,

I am linking a  table from sharepoint directly to a report online. In the table is a column with the Date in the follwing format: dd/month/yyyy, 31/May/2018 for example.

However, when this variable is used, the repor reads it as a text which causes problems when trying to graph the evolution of a given variable over time.

I know that in the desktop version I could easily change the format of a variable so it is read as date. However, how is this done in the online report?

Any ideas?

Many thanks

Andres