“Maybe he changed it,” she offered.

“Maybe.” But a changed date usually erases the old one.

This one had both, sitting side by side, and that is not revision; that is carelessness, or something worse than carelessness.

In my work, a document with two conflicting dates is rarely a mystery for long.

Either someone was sloppy, which happens, or someone assembled a thing quickly from parts that did not match, which happens too and means something different.

A real company revising a real schedule issues a clean new document; it does not leave the old date sitting beside the new one like a fingerprint.