When you are in the project administration section, you can view all of the versions for a project. If there is a date associated with the scheduled release of the version prior to the version being released, then when you click release it defaults to the prior day. I would expect the behavior to use the day submitted in the field to populate the calendar field.
Updating the date and saving works fine, this only affects the initially displayed date. If you don't have a release date and click release the field is empty and you have to select it. So this only impacts us when we have a planned release date for the version.