…的时候: when, while
固定格式 / fixed patterns
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
Clause / Noun + 的时候，Main clause
To say "when…", Chinese puts the time clause first, followed by 的时候: 我小的时候 = when I was little.
Unlike English, where "when…" can come last, in Chinese the time clause comes before the main clause.
在 can be added in front for a more formal style: 在吃饭的时候.
Examples
过春节的时候，我们一家人一起吃饭。
Guò Chūnjié de shíhou, wǒmen yì jiā rén yìqǐ chī fàn.At Spring Festival, the whole family eats together.
我小的时候很喜欢放鞭炮。
Wǒ xiǎo de shíhou hěn xǐhuan fàng biānpào.When I was little I loved setting off firecrackers.
吃饭的时候别看手机。
Chī fàn de shíhou bié kàn shǒujī.Don't look at your phone while eating.
你有空的时候给我打电话。
Nǐ yǒu kòng de shíhou gěi wǒ dǎ diànhuà.Call me when you're free.
Common mistakes
✗ 我很喜欢放鞭炮的时候我小 → ✓ 我小的时候很喜欢放鞭炮.
✗ 当我小 (without 的时候) → ✓ 我小的时候.