1190.52 – Day Before Yesterday

When the day before yesterday was referred to as the day after tomorrow, the day that was then called "yesterday" was as far away from the day we now call "tomorrow" as yesterday is from the day on which we shall be able to speak of last Monday as "a week ago yesterday."

What day of the week is it if the above statement is true?

Solution

Guess and check. Make a grid like this one and put an $x$ (today) in some space in the middle week.

Then put $d$ in as the day when "the day before yesterday" was referred to as "the day after tomorrow;" $d$ will be 4 days before x.

Then set $c_1$ as the day before $d$ ("the day that was then called yesterday") and $c_2$ as "the day we now call tomorrow."

Then set $k_1$ as the real yesterday (right before $x$ ) and set $k_2$ as "the day on which we shall be able to speak of last Monday as 'a week ago yesterday.'"

Compare the distances $c_1c_2$ and $k_1k_2$ to see if $x$ is on the right day. (Putting $x$ on Thursday works.)