1997 (real world)

1997 is the year Halo started development.

Prior to September 24

 * Halo started development under the initial codename "Armor".

September

 * September 24: The trademark for Halos first codename "Armor" was filed.

After September 24

 * Bungie worried that "Armor" was boring and changed Halos codename to "Monkey Nuts", knowing it had to be changed later.