How can I change the date format in ticket view?

Short answer: you can't. The date display cannot be changed, and last I saw, there's no plans to change that.

If for your customer side, you somewhat can. In your help center you can edit the code for your theme. In the requests_page.hbs file you will find the section for the requests table. In the table body section are the lines for the meta-data referencing the date created_at and updated_at. Change the timeago=true to timeago=false, and add format='long'. You can use short in place of long for the date format you mentioned, but that leaves out the time. Long should get you closest to what you are aiming for, I think.