What's the difference between sempiternal and sempiternity?

Sempiternal

Definition:

• (a.) Of neverending duration; everlasting; endless; having beginning, but no end.
• (a.) Without beginning or end; eternal.

Example Sentences:

• (1) So Zhou Enlai’s famous reply was actually quite banal – yet is now universally reinterpreted as a gem of sempiternal Chinese wisdom.

Sempiternity

Definition:

• (n.) Future duration without end; the relation or state of being sempiternal.

Example Sentences:

• (1) So Zhou Enlai’s famous reply was actually quite banal – yet is now universally reinterpreted as a gem of sempiternal Chinese wisdom.