What's the difference between dateless and sempiternal?

Dateless

Definition:

• (a.) Without date; having no fixed time.

Example Sentences:

• (1) In Audi’s “Prom” ad , a dateless teenager is inspired to steal a big kiss at the big dance after his dad loans him the new A6.

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.