dateless vs undated

dateless and undated both are adjectives.

Word	Noun	Adjective	Verb	Adverb
dateless	No	Yes	No	No
undated	No	Yes	No	No

As adjectives, dateless and undated are synonyms defined as:

dateless (adjective)	undated (adjective)
having no known beginning and presumably no end	not bearing a date
unaffected by time
not bearing a date
of such great duration as to preclude the possibility of being assigned a date