dateless

1. having no known beginning and presumably no end;

"the dateless rise and fall of the tides"

"time is endless"

"sempiternal truth"

2. of such great duration as to preclude the possibility of being assigned a date;

"dateless customs"

3. not bearing a date;

"a dateless letter"

4. unaffected by time;

"few characters are so dateless as Hamlet"

"Helen's timeless beauty"