Got iPhone, iPad or iPod touch that's been bricked by the '1 January 1970' date bug? Well, there's a fix - briefly unplug the battery. Unfortunately, it means taking your device apart, so it's not without risk and not for those who value their warranty or aren't confident spinning a screwdriver.
Here's a video showing the process on the iPhone.
For other iOS devices I suggest you take a trip over to iFixit and pull up the instructions to replacing the battery inside your device.
Alternatively, you can wait until the battery goes flat, which should accomplish the same as removing the battery, although it will take a long time since the device isn't being worked hard on the bootup screen.