This article describes how to manually edit the time and date.
INSTRUCTIONS & INFO
Time and date are set automatically on the Kindle Fire HDX.
To set the time zone on the device, from any screen, swipe down from the notification bar.
Tap Settings.
Tap Device Options.
Tap Date & Time.
Tap Select Time Zone.
Select the desired region and time zone to edit the date & time. Note: Amazon Kindle automatically sets the date and time according to the region and time zone.