I try to make a difference between two dates, but displaying the days and hours. So I found a good idea on this website : https://sharepointonline.wordpress.com/2012/03/02/date-time-duration-using-calculated-field-column/
I have adapted my code with my start time column Debut Diag and my end time column Fin Diag :
=DATEDIF([Debut Diag],[Fin Diag]-(MOD([Debut Diag],1)>MOD([Fin Diag],1)),"d")&" Day(s) "&TEXT(MOD([Fin Diag]-[Debut Diag],1),"hh"" Hour(s) ""mm"" Min(s)""")
Tried with h instead of hh too
But I get an error SharePoint, that explains nothing or gives no idea of the problem. Maybe I have a syntax error, or the way can't work. Can you tell me what do you think?