kasniti
be late - but that's an adjective, it's a property; "kasniti" is a verb denoting an action. Besides, being late is often used for the dead, the difference being only in the article: "the late postman" is a deceased postman, "the postman is late" is what he's doing, running behind schedule
run late - almost there, except that it should apply to things which can't possibly be running
be behind schedule - same misgivings as for "be late", plus the number of things/events which may kasniti is larger than the number of those which have schedules