See (https://support.docusign.com/en/guides/ndse-user-guide-time-and-date) this article for how to update your date format . Please note that this is an account wide setting so it will affect all envelopes created from then onward. Unfortunately you cannot change the date format on an individual field basis within DocuSign. 

Hope this helps

Thank you for your answer Andrew. I've already had followed inscructions of this article. However, when my recipient signs, the date is still formated like DD/MM/YYYY instead of YYYY-MM-DD.

Was the envelope in question sent before the change was implemented? The change wouldn't affect any open envelopes, only those created afterward.

If it was created after the switch . . . I'll run some tests and get back to you.

Are you trying to change the format of the date signed tag? If so, you can adjust the format in your admin console on the Signing Settings page in the Document Formatting section.

Having options for format of date signed on an envelope-by-envelope basis is a must. If DocuSign does not already have on its development list, it's time to add it! I'm reading posts from a year ago. Tragic.

This is still an issue for me, 4 years later, I guess.