I used to live next to a town where a pair of notorious identical twin sisters lived. Their names are Emma and Sophia. Emma always lies on Monday, Wednesday, and Friday; on other days of the week she always tells the truth. Sophia always lies on Tuesday, Friday, and Saturday; on other days of the week she always tells the truth.
The other day I met the twins, and asked one of them:
- Who are you?
- I am Emma.
- What day is today?
- Yesterday was Sunday.
The other twin added:
- Tomorrow is going to be Friday.
I was surprised — how could it be — and asked her:
- Are you telling the truth?
And she said:
- I’m always telling the truth on Wednesdays.
The twins got me confused, but after a while I figured out who was who, and I even figured out what day it was.
Can you?