Version's release date is off by one day if client's workstation time zone is at least +1 compared to the server's timezone Confluence is running on.
Steps to reproduce:
Open Confluence from a PC that has a timezone set to +1 compared to Confluence's server (e.g. if Confluence's server is set to GMT+1, use a PC with GMT+2 or higher)
Go to a space with Scroll Versions activated
Choose a version -> Edit
Add a release date for a version: 12/31/15
After saving the release date is 12/31/15
After saving the release date is 12/30/15
Setting any timezone in the user's Confluence profile doesn't affect anything.