届时
when the time comes; by then; at that time (formal)
Structure
（将来的）时间／事件 ， 届时 ＋ 安排／情况
What it means
Formal ‘when the time comes, by then’: 届 is ‘to arrive (at a set time)’, and 届时 points back to a time already named, usually in the future.
How it is built
Future date/event + ，届时 + arrangement: 大会定于10月10日召开，届时将有两千多名代表参加 (over 2,000 delegates will attend then).
When to use it
Notices, invitations and news; in speech say 到时候. In a past story it can point to a time then still ahead: 原定24日出水，可天气预报说届时会有冷空气南下.
Watch out
Not a plain past ‘at that time’: ✗1987年，届时… ✓1987年，当时…. It needs a time already named before it.
Examples
博物馆下个月重新开放，届时将展出一批新出水的文物。
The museum reopens next month, when a batch of newly recovered relics will go on display.
大会定于10月10日召开，届时将有两千多名代表参加。
The conference is set for 10 October, when more than two thousand delegates will attend.
比赛如果改期，我们会提前通知，届时请留意短信。
If the match is rescheduled we will let you know in advance, so please watch for a text message then.
Learn this in Lesson 176 · HSK 7–9: 南海一号 (The Nanhai No. 1 shipwreck)
A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.
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