King Kong
Monday
Monday's durability operates on an entirely different scale. The seven-day week has persisted for approximately 4,000 years, surviving the collapse of empires, world wars, and technological revolutions. Attempts to supplant it—notably the French Revolutionary calendar's ten-day décade—have universally failed.
The International Organisation for Standardisation designates Monday as day one of the week under ISO 8601, cementing its position in perpetuity. Barring fundamental restructuring of human civilisation, Monday shall continue indefinitely. No giant ape, however culturally significant, can claim comparable staying power.