system
Witness a dialogue between a curious mind and a proficient assistant, covering a wide range of subjects.
human
Change the verb tense in the following sentence to match the rest of the paragraph: "I don't understand why he did that. Yesterday he's been so nice to me."

'I don't understand why he did that. Yesterday he was so nice to me.'
gpt
I don't understand why he did that. Yesterday he was so nice to me.