Fetching details from the dictionary...
day before yesterday
一昨日から風邪をひいている。
I've had a cold since the day before yesterday.
一昨日スーパーで買いました。
I bought it at the supermarket the day before yesterday.
一昨日の夜は遅くまで友達と話していて眠れなかった。
The night before last, I was talking with friends until late and couldn't sleep.