three days from today; the day after tomorrow's tomorrow (i.e., two days after tomorrow).
明々後日にまた会議がありますので、資料を用意してください。
We have another meeting three days from now, so please prepare the materials.
その映画は明々後日に公開される予定だ。
That movie is scheduled to be released in three days' time.
しあさっては忙しいが、明々後日は空いていますか？
I'm busy the day after tomorrow; are you free three days from now?