Yesterday
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.
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.
it will be the third day from today (or the day after tomorrow).
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.
Friday
Thursday
Saturday.
The day before today. Two days before tomorrow. But if tomorrow never comes, will yesterday ever go. =/ At the time of this writing, yesterday was Sunday, January 1st, 2011.
Tomorrow.
Sunday
4
Friday