2 sentences for 凑 (còu — happen by chance)

1. 时间正好凑在他休息那天，我们可以一起去。

   shí​jiān zhèng​hǎo còu zài tā xiū​xi nà tiān, wǒ​men kě​yǐ yī​qǐ qù.

   The timing happens to coincide with his day off, so we can go together.

   Source: Dong Chinese Dictionary

2. 我刚准备去车站你就打来电话，时间真是凑得正巧。

   wǒ gāng zhǔn​bèi qù chē​zhàn nǐ jiù dǎ​lái diàn​huà, shí​jiān zhēn shì còu de zhèng​qiǎo.

   I was just about to head to the station when you called; the timing was perfect.

   Source: Dong Chinese Dictionary