Hi,
On the device ensure within "Options > Date\Time" the time zone, date and time settings are correct. Also check the time source to ensure it is set the same as other users who don't have any issues. As this is a device only issue it would be worth comparing the firmware version to other 8310 users (if you have any). Once you check the setting restart the phone by removing the battery and try sending\replying to a few test emails to see if the issue persists.
Thanks,
Gary