Rustc version does not match manifest version

[Diggsey]

Often the date given by rustc --version is the day before the date on the manifest. Also the date given by cargo --version often does not match one or both of those dates.

This is confusing for users installing a specific version of rust, and it makes referring to a nightly by date ambiguous.

Ideally there would be a mechanism to ensure that regardless of when the components are built or packaged, they all agree on the date given by --version and the manifest date.

[Diggsey]

This is causing confusion for people on IRC on almost a daily basis 🙁

[jyn514]

This is a duplicate of #51533 (which was opened later but has more discussion).