Changing date in report column from dd/mm/yyyy to dd/mm/yy

Summary

Change from 4 digit year to 2 digit year

Content

In Edit Definition I have tried date_format(fieldname,'DDMMYY') but it stopped showing the date and just repeated the column name.

I want to just change dd/mm/yyyy to dd/mm/yy and preferably for the whole report rather than column-by-column if that is possible.