Monday
In terms of operational consistency, Monday represents perhaps the most reliable phenomenon in human experience. Since the adoption of the seven-day week by the Babylonians approximately 4,000 years ago, Monday has arrived without fail, without delay, and without exception.
No force in nature or human ingenuity has successfully prevented a Monday from occurring. Leap years, calendar reforms, and global pandemics have all failed to disrupt this inexorable cycle. Monday's coefficient of reliability stands at precisely 1.0, a mathematical certainty unmatched in the natural world.