too late to be useful; a day late and a dollar short
Idiomatic expression referring to something that arrives or is done after the critical moment, rendering it useless. Literally, a chrysanthemum blooming on the 10th, one day after the Chrysanthemum Festival (重陽の節句) on the 9th day of the 9th month.
See also: 重陽
Coming to help now is too late to be of any use.
That advice came a day late and a dollar short; I had already made my decision.