I accidentally backed up my 8700g (os 4.5, DM 4.6) while it was locked.
On completion of backup, I went in to change the time zone as it always reverts to the original and throws my calendar etc out, but this time all stayed as it was before the backup.
So, by keeping the 8700g locked while backing up, seems to fix the 'revert to original time zone on backup' problem. :D