As reported on the Unity forums, adding packages from the Github npm package registry produces the following error on Windows:

Cannot perform upm operation: EINVAL: invalid argument, utime
It turns out this caused by the publish dates that Github uses for newly published package versions: 0001-01-01T00:00:00.000Z

This is likely on error on Github's part since this is not an accurate publish date but it should not cause the Package Manager to fail. We should treat invalid dates the same way we treat missing publish dates, which is a use case we support.

Repro steps:

Follow this guide to create a package that can be published to the Github npm package registry
From the package folder, run npm publish
In the Unity editor, go to the Package Manager window
Click the "+" icon and "Add package by name"
Enter the name of the package you published to the Github registry
Expected behaviour:

The package should be added to the project.

Actual behaviour:

Adding the package fails with the error Cannot perform upm operation: EINVAL: invalid argument, utime