Emphasising details with 是…的 — Chinese grammar (HSK 3)

Subject + 是 + Time / Place / Manner + Verb + 的

When an action has already happened and you want to highlight when, where or how it happened, wrap that detail in 是…的: 我是昨天到的 stresses "yesterday". The action itself is old news; the detail is the point. 是 can be dropped in casual speech, but 的 at the end stays.

Examples

我是昨天到的。 Wǒ shì zuótiān dào de.	It was yesterday that I arrived.
他是坐飞机来的。 Tā shì zuò fēijī lái de.	He came by plane.
你是在哪儿认识她的？ Nǐ shì zài nǎr rènshi tā de?	Where did you meet her?

Tip: 是…的 only works for completed actions, so never combine it with 了.