Xiànzài bù hǎohǎo fùxí, dào shíhou jiù láibují le.
If you don't revise properly now, by then it'll be too late.
Tips
usage
到时候再说 'we'll see when we get there' is the classic way to put off a decision. 届时 is the formal written equivalent used in notices, and 到时 is a shorter form.
