Hi,
Using Jira Cloud, I click Release button at the top right of my Kanban Board, I enter a Version name, and a release date 18/Jun/18 (can't remember if I used the calendar control, or if it was filled by default).
I then click the blue Release button.
I then go to the Releases page.
The release is shown, but the date is wrong: 17/Jun/18
My web browser (latest Chrome is set to accept language en-us first, my local computer is set to UTC+0 London with day light savings. I clicked the release button at about 10:30-11:00 my local time. This has happened for the last few weeks for me and others in my company, and I always blamed the user for picking the wrong date in the date picker. It's not. Jira changes the date for us. It seems like a bug.