DNR Garmin had the ability to select the timezone for local time calculations from the Units tab. DNRGPS has the appropriate setting value in dnrgps_properties.xml but does not appear to have any GUI to edit the values held there.
I cannot make it use anything but local computer time. I've tried copying various values out of the DNRGarmin registry settings and pasting into the users dnrgps_properties.xml but so far nothing has changed.
Without this my ltime field is always out by 10 or 11 hours (Sydney, Australia).