In English, we might say It was yesterday that she left to add emphasis to yesterday. In Chinese, you can do this by saying 是 (shì, to be) after the person and then adding 的 (de, show possession) to the very end. You normally only do this when talking about the past.
他们是去年春天去伦敦的。
Tāmen shì qùnián chūntiān qù lúndūn de.
It was spring last year that they went to London.
我们是三天前到的。
Wǒmen shì sān tiān qián dào de.
It was three days ago that we arrived.
If you’re asking a question, just add 吗 (ma) after 的 (de)!
你是上个月走的吗？
Nǐ shì shàng gè yuè zǒu de ma?
Was it last month that you left?
The day before yesterday and the day after tomorrow in Chinese are just 前天 (qiántiān) and 后天 (hòutiān). Easy peasy!
前天是我的生日。
Qiántiān shì wǒ de shēngrì.
The day before yesterday was my birthday.
我的猫前天喝了我的咖啡。
Wǒ de māo qiántiān hēle wǒ de kāfēi.
My cat drank my coffee the day before yesterday.
后天你会做什么？
Hòutiān nǐ huì zuò shénme?
What will you be doing the day after tomorrow?
If you want to talk about seasons, don’t forget to use 天 (tiān, day) after the season word!
这个春天我们会有一个新的老师。
Zhè ge chūntiān wǒmen huì yǒu yí ge xīn de lǎoshī.
This spring we will have a new teacher.
这里的夏天有多热？
Zhèlǐ de xiàtiān yǒu duō rè?
How hot are the summers here?
她去年秋天来了北京。
Tā qùnián qiūtiān lái le Běijīng.
She came to Beijing last fall.
你喜欢冬天吗？
Nǐ xǐhuān dōngtiān ma?
Do you like winter?