Hello @Hugo_Dupont,
As per your current implementation, I recommend you first use the parseDate() function and then use formatDate().
Also, try to get the day of the week.
These tokens help you https://www.make.com/en/help/functions/tokens-for-date-time-formatting
Check this related topic and its answers.
If this is still not solved, share details with screenshots.
P.S.: Always search first, Check Make Academy. If this is helpful, Mark Best as Solutions 
and give 
If you need expert help or have questions? Contact or comment below! 