From the original JRA issue:

There are currently some odd behaviours if the client-side system time is behind.

• To reproduce, modify system time on client
• create a new issue ticket
• In JIRA Agile, columns will show "-1 days in column", instead of "0 days"

Although the above is to manually reproduce the problem, it can occur with NTP-adjusted systems where the time is a bit off.

The time data stored into the database is not affected, this is purely a display issue on the client side.