sempiternal vs endless

sempiternal and endless both are adjectives.

Word	Noun	Adjective	Verb	Adverb
sempiternal	No	Yes	No	No
endless	No	Yes	No	No

As adjectives, sempiternal and endless are synonyms defined as:

sempiternal and endless: having no known beginning and presumably no end

Other synonyms of sempiternal include dateless.

sempiternal (adjective)	endless (adjective)
having no known beginning and presumably no end	having the ends united so as to form a continuous whole
	having no known beginning and presumably no end
	tiresomely long; seemingly without end
	infinitely great in number