Hello Karen,
Thank you for reaching out to us!
Unfortunately, changing the display format in bulk is not something our "Dataset Design Editor" supports. Changing the display format on the folder level is a great idea and should work.
- What version of LabKey are you using?
- What was the format string you specified on the folder level?
You can use https://www.labkey.org/Documentation/wiki-page.view?name=dateFormats as a refernce for what format strings can be used.
Thanks,
Chet