1.  How is this data stored in SQL?  Which SQL data type is being used?

2.  Which SmartObject Property type is in use?  Date or DateTime?

3.  Is the SQL server and K2 Server/K2 Web Server in the same time zone?

4.  If the Client Browser and K2 Server/K2 Web Server in the same time zone?

Might be caused by differences in the server and user time-zones.  I've seen this happen when a Date is stored in a SmartObject and displayed using a DateTime field with formatting to display only the date part.  What happens is that K2 adds a time of midnight to the date when assigning it to a DateTime field.  This is midnight relative to the server.  When this DateTime is sent to the user (who is further "west" of the server), the DateTime is converted to the user's local date/time (which is yesterday sometime).  But since the time isn't being displayed, it appears that the date is one day off.

Example:  User 2 time-zones "west" of the K2 Server

Date in SmartObject: 1/5/2016

Date/Time reported by server:  1/5/2016 00:00:00

Date/Time for the local user:  1/4/2016 22:00:00

Date seen in DateTime field with date-only formatting:  1/4/2016

In my case, the solution was to change the date type of the control to be Date instead of DateTime.