How Many Fridays Are There in February?

Question

What is the greatest and least number of Fridays in February?

Answer

The usual answer is that the greatest number is five — the least, four. Without question, it is true that if in a leap year February 1 falls on a Friday, the 29th will also be Friday, giving five Fridays altogether.

However, it is possible to reckon double the number of Fridays in the month of February alone. Imagine a ship plying between Siberia and Alaska and leaving the Asiatic shore regularly every Friday. How many Fridays will its skipper count in a leap-year February of which the 1st is a Friday? Since he crosses the date line from west to east and does so on a Friday, he will reckon two Fridays every week; thus adding up to 10 Fridays in all. On the contrary, the skipper of a ship leaving Alaska every Thursday and heading for Siberia will “lose” Friday in his day reckoning, with the result that he won’t have a single Friday in the whole month.

So the correct answer is that the greatest number of possible Fridays in February is 10, and the least – nil.

 

From Astronomy for Entertainment –  Yakov Perelman