NOTE: There is always a possibility your game data can be corrupted, so do this at your own risk!

Start a game in the Temple of Time, then gently and SLOWLY pull up on the left side of the game cartridge. If you do it slow enough, the computer will become lagged, Link will jump all over the screen, and the sound will become very corrupted. If you let this happen for a few seconds, the N64's processor will become lagged and the game will lock up; there's going to be a small yellow bar that will appear in the top-left of the screen. When you get the small yellow bar to appear, there are some commands that you need to input on the controller to get the "debug" code to appear on the screen. This will also show the time and date that your particular game was made. Enter these button combos to make the code appear onscreen:

1: L + R + Z
2: Control Pad Up + C-Down
3: C-Up + Control Pad Down
4: Control Pad Left + C-Left
5: C-Right + Control Pad Right
6: A + B + Start

The debug/error code won't be shown unless you push each button listed. Example: in the first step, you must push the Z button while HOLDING the L and R buttons.