The commit and author date and name are always set whenever you commit (this is a Git requirement); they default to "now" and whatever you set your committer identity to.
Those checkboxes are only relevant if you:
- want to set the commit date to anything but "now"
- want to change the author identity of the commit when you amend the previous commit (usually, only the commit identity is set to yours, but the author identity is left alone).