adjective Affected or overtaken by the lateness of the time; hence, synonym of benighted (“overtaken by night; caught out by oncoming night before reaching one's destination”).
adjective Later in relation to the proper time which something should have happened; specifically, delayed beyond the proper time.
A belated happy birthday to you!
adjective Slow to learn or to adopt a trend; hence, lacking education or sophistication; benighted, unenlightened, unsophisticated.