Trapped! system preferences time date error

Question

I changed the date on my mac mini to 1987 by accident.
The system preferences app is now locked.
I have tried to use a sudo date in Terminal, however this requires password to complete command.  My administrator password is blank so it cant process this.
I cant change my administrator password the usual way as this is done through system preferences which is also blocked (to access users and groups, as well as date/time settings)
the system preferences box does open, but it gets stuck loading any of the icons so needs force quit
(ive tried 32 bit enabled but didnt work)
Help much appreciate Im completely trapped at present.
Liam

Answer 1

Start up in Recovery mode by holding down the key combination command-R at the chime.
Select Get Help Online. Safari will launch. While in Recovery, you'll have no access to your bookmarks, but you won't need them. Load this web page.
Triple-click anywhere in the line below to select it:
date 0801000014
Copy the selected text to the Clipboard by pressing the key combination command-C.
Quit Safari. You'll be returned to the OS X Utilities screen.
Select
          Utilities ▹ Terminal
from the menu bar. A Terminal window will open. Paste into the window by pressing the key combination command-V.
Wait for a new line ending in a dollar sign ($) to appear below what you entered. If it doesn't appear, press return.
Quit Terminal to return to the main screen. Try the installation again.