RFC for the 7XX Range of HTTP Status Codes – Developer Errors (github.com)

I feel like there should be a category for "temporal anomalies" in there.

    7x1 - This hasn't happened yet.
    7x2 - This already happened.
    7x3 - Grandfather paradox
    7x4 - Chronic Hysteresis
    7x5 - Time War
    7x6 - Time Lock
    7x7 - Bad Wolf
    7x8 - Silence Will Fall

etc...