Zuótiān wǎnshàng vs. Zuó wǎn

Rocket Chinese (and other language courses) seems to prefer "zuótiān wǎnshàng" (昨天晚上) for saying last night. Google Translate thinks "zuó wǎn" (昨晚) is sufficient. Which one is the best way to say last night? Is the second (zuó wǎn) correct or less desirable?

你好！ 昨晚 is a more formal way of saying last night and is rarely used in everyday speech. One this to watch out for in Chinese is the shortening of words and expressions, they are often the formal versions that you may see in letters, newspapers or formal documents. It is important to recognise them but at the same time be aware that the longer versions are more likely to be used in everyday speech. I hope this helps and keep up the good work! - Lin Ping

That helps - thank you for the explanation.