I know for a Tree Definition of DataElementFolder, there is a DateFormat attribute, but the DataElement node doesn't have such an attribute.
<DataElements Type="MA.PressRelease.Article" Label="${C1:Data:MA.PressRelease.Article:Date}" Display="Auto">
This will show up looking like this.
It would be nice to have something like "Month day, Year" (Ex: May 4, 2017)
https://github.com/Orckestra/C1-CMS-Foundation/issues, open a new issue, starting with the Title "Feature Request:" make a clear explanation about the benefits and anything else that you think that would improve and wait for response.