According to a post on Reddit and reports out of China, it is possible to brick an iPhone by setting the date back to a specific time.
I wasn't brave enough to test it myself, but the post claims the bug only affects 64-bit iOS devices.
It would seem that changing the device's Date & Time values to a specific point in time would cause it to fail to boot properly.
Basically, it gets bricked and stuck at the Apple logo boot image. Neither DFU mode nor restoring from a backup would bring a bricked device back to life as a physical repair is required to put it back into working order.