JIRA v6.3.8, JIRA Agile v6.6.13
1. Go to project Overview>Versions (or project Administration>Versions) and observe a release date for certain version (in my example on the screenshot1.jpg it will be 22/Jan/15)
2. Go to appropriate Agile board where this release will be represented, expand versions from the left, and observe the date of the same release
—
Release date will be shown one day back (in my example on the second screenshot2.jpg it will be Release Date: 21/Jan/15)

Steps to Reproduce

We simply need to make JIRA's "Default user time zone" mismatch with Java's recognized "System Default". Let's assume the current Java "System Default" is: America/Los_Angeles (GMT -7)

Reproduce 1

1. Create a new Agile board, using the Sample Scrum Project
   • This will automatically include versions with release dates
2. Within JIRA, modify JIRA Administration > System > General Configuration > Default user time zone
3. Change the region to "Australia" and "GMT +8"
4. Now compare the version dates on the Agile Board vs. the Project administration page - notice that they are a day off

Reproduce 2

1. Modify the JVM parameters to include: -Duser.timezone=Australia/Perth
2. Restart JIRA and compare versions

Workaround

Ensure that both "Default user time zone" and JVM timezone match