dateless
1. [ adjective ] not bearing a date
Synonyms: undated
Examples:

"a dateless letter"

Related terms: undatable
2. [ adjective ] of such great duration as to preclude the possibility of being assigned a date
Examples:

"dateless customs"

Related terms: undatable
3. [ adjective ] having no known beginning and presumably no end
Synonyms: sempiternal endless
Examples:

"the dateless rise and fall of the tides" "time is endless" "sempiternal truth"

Related terms: infinite
4. [ adjective ] unaffected by time
Synonyms: timeless
Examples:

"few characters are so dateless as Hamlet" "Helen's timeless beauty"

Related terms: unaltered