[masswerk]

Prefixing octal numbers by zero was a common convention. The real dumpster fire was all those intermediate years without an octal notation in strict mode. (If you needed them, either forget strict mode, or choose between converting to meaningless decimals or using strings and feeding them through parseInt. What's sane about this?)

However, 058 should have been a parse error.

[tempodox]

I agree. That inconsistency in how the `0` prefix is handled shouldn't exist.