Dateless
Part of speech: adjective
Definition: Out of one's head; deranged. thick-headed Without a date imprinted, assigned, or associated. Having no date—a meeting with a lover or potential lover. Timeless; immortal Without a start; immemorial Without an end; endless
Undatable
Part of speech: adjective
Definition: Not able to be dated; that may be not be ascribed a date (or age).