I hadn't used my 310XT for a while, and the battery had completely discharged. Having recharged the battery, I did an indoor activity and then saved it. When I uploaded the activity using Garmin Express and the ANT stick, it didn't seem to upload.
After reading this thread, I tried doing a Settings->Transfer All a few times but to no avail. I looked in the Application Support folder but could only see two files from 2007 during the sync there that for sure were nothing to do with my problem. I tried recording a test activity, but had the same problem.
As recommended in the same thread, I then I found a copy of the Garmin ANT Agent software on another site, installed this, removed the 310XT from Garmin Express, and tried to synchronise. It did the synchronisation okay, and seemed to copy the files and transfer them to Garmin Connect, but they were still not apparent in GC. Then I tried to record yet another test activity, and after saving it, looked through the activity history and noticed that my earlier indoor activity was now recorded with a date in 2007 rather than "Today" as was visible previously. I found the activity at the end of my history in GC, changed the date and then all was well.
I had turned GPS off during these attempts to upload, so I am more or less certain that the date synchronisation was due to the ANT Agent and not the 310XT getting a GPS fix, and in any case, having a GPS fix previously had not updated the clock on the device, as happens with newer Garmin watches. I presume that the clock is only updated when an outdoor activity is performed?
So to conclude:
- After the 310XT was fully discharged, it forgot the current date and time. Since I had not used the GPS since recharging it, the date and time was just a few days later than the default of 31/3/2007 (3/4/2007 in my case)
- Garmin ANT Agent appears to synchronise the date/time on the device with the current date
- The clock on the 310XT only seems to be updated when performing an outdoor activity
- Garmin Express does not synchronise the date and time on the device with the current date and time
The problem then is that GE should synchronise the date on the device to be backward compatible with the ANT Agent.