到时候 (when the time comes)

We'll decide then

• Your friend asks what you'll do if the flight is cancelled next month.
• when the time comes到时候dào shí houto say again再说zài shuō(suggestion)吧ba。 — "Let's deal with it when the time comes."

when the time comes到时候dào shí hou = when the time comes, then

• when the time comes到时候dào shí hou refers to a future moment already mentioned or understood: the trip, the exam, the meeting.
• It usually starts its clause: when the time comes到时候dào shí houI我wǒto给gěiyou你nǐwill call打电话dǎ diàn huà.

when the time comes到时候dào shí houI我wǒto给gěiyou你nǐwill call打电话dǎ diàn huà。

Plans and warnings

• you你nǐnow现在xiàn zàidon't不búrevise复习fù xí，when the time comes到时候dào shí houthen就jiùtoo late来不及lái bu jí(completed / change)了le。 — "If you don't revise now, it'll be too late when the time comes."
• next week下周xià zhōuto hold a meeting开会kāi huì，when the time comes到时候dào shí houeveryone大家dà jiāall / both都dōuwant / will / need要yàoto make a speech发言fā yán。 — "We have a meeting next week; everyone will have to speak then."

you你nǐnow现在xiàn zàidon't不búrevise复习fù xí，when the time comes到时候dào shí houthen就jiùtoo late来不及lái bu jí了le。

Future only

when the time comes到时候dào shí hou versus at that time当时dāng shí

• at that time当时dāng shí = at that time (past): at that time当时dāng shíI我wǒstill还háivery很hěnyoung小xiǎo.
• when the time comes到时候dào shí hou = then (future): when the time comes到时候dào shí houyou你nǐthen就jiùto know知道zhī dào(completed / change)了le — "You'll know when the time comes."

at that time当时dāng shíI我wǒstill还háivery很hěnyoung小xiǎo。

Recap

Read the full reference: HSK 6 grammar — Adverbs.