[ Arithmetic. Mental calculation, etc.]

When "the day after tomorrow" becomes "yesterday," then "today" will be as far from Sunday as the day that was "today" when "yesterday" was "tomorrow." What day of the week do you think it is today?
Think about how many days separate "today" from the day when "the day after tomorrow" becomes "yesterday".

## Solution

By direct verification, we can see that 4 days pass between the day when "yesterday" was "tomorrow" and the day when "the day after tomorrow" becomes "yesterday." Therefore, the days we are interested in cannot be equally distant from the same Sunday, but only from two different ones. This is possible if the first day is Monday, the second day is Saturday, and today is Wednesday.

## Problem