When exporting the data to a format readable in Excel, there are columns of SensorDisplayTime, SensorInternalTime, MeterDisplayTime, MeterInternalTime. What information are they providing? I know how to convert the data shown the date/time in Excel.
I suspect the following - The Receiver is shipped with an internal time set, likely to GMT time, that is not impacted when you enter date/time to be your local time. So it is keeping track of the 2 times separately, which helps for example when there is a switch for daylight savings time. The internal/GMT time just keeps ticking without gaining or losing an hour, so that the trend arrows and calibration reminders can stay on track.
When the a sensor reading is sent to the receiver, it records the value, the internal time and the local time. That would be in the export file under the columns SensorInternalTime, SensorDisplayTime and SensorValue. When you do a calibration using a BG from your meter, it again records 3 columns - InternalTime that meter read was entered, the local time, and the MeterValue.
If you enter events, like exercise, insulin, there is another set of columns for that.
When displayed on the Dexcom software, it would likely show the data using the local time, but that's an interesting thought - I'll have to check what happened during the last time change !
Yes, the MeterInternalTime is in GMT time. I wrote the import routines for ManageBGL.com, and yesterday we tested with a sample Dexcom file that had both meter reads and sensor data in it. The resulting charts look great, but we'd also like to try with one that has insulin, exercise and other data. Would you be happy to send us one? (or create an account at ManageBGL.com and upload it)?