The day before tomorrow is called "today." Therefore, two days before tomorrow would be "yesterday." This is because each day progresses linearly in a chronological sequence, with yesterday being the day that comes before today, and tomorrow being the day that comes after today.
Yesterday
Two Days Before the Day After Tomorrow was created on 2005-10-19.
Friday
Today is Sunday. Monday is the day before two days after today (the day before tomorrow). Monday is the day before Tuesday. Two days after today is Tuesday.
Tomorrow
Tomorrow
Saturday.
Two days before the day after tomorrow
Tomorrow.
Sunday
To solve the riddle, we start from "the day after the day after tomorrow," which is two days from today. If that day is four days before Monday, then two days from today is Sunday (since four days before Monday is Thursday). Therefore, today is Friday.
The day must be Thursday because "the day after tomorrow" means two days into the future and two days before Sunday is Friday. that means that yesterday would have been Thursday.