TimeZoneMapper warnings in Foldering logs

We are seeing a bunch of warnings of the following form in the WFB Foldering logs:

2013-11-14 08:40:21,861 WARN [http-9101-19] TimeZoneMapper: No timeZoneId found for udsTimeZonePref null. Defaulting to US/Central.

Is anyone familiar what setting we are missing that causes this warning?