Contacted Garmin support on the 21st Dec with a description of the problem. Over 3 weeks later and still no response (even though they say they'll get back to you within 3 business days). Just sent another support request. Not good enough Garmin.
Note, i've discovered that activities post with the correct time and date if i upload directly through my computer (Garmin Express). The date/time issues (+11 hours for me) only appear if i upload through the Connect iPhone app.
Not sure what other's experiences are or if you've found a solution. I was hoping they'd have fixed this by now.