In the U.S., we often write dates such as July 4, 1776, as 7/4/76. In other countries, the month is given second and the same date is often written as 4/7/76. If you do not know which system is being used, how many dates in a year are ambiguous?

Question

144
132
100
Depends on leap year

Explain how you arrived at that answer.

Answer 1

If one of the numbers is greater than 12, there is no problem, that cannot represent a month.

so any day with 1 to 12 in either the first or second position, or 12 x 12 = 144
BUT, dates like 1/1/76, 2/2/76, ... 12/12/76 pose no problem

so the number which are ambiguous = 144 - 12 = 132

(I often run into this problem up here in Canada when dealing with correspondence with the US, but not with correspondence from anywhere else.
We have had cases where Canadians who had to buy extra health insurance while traveling in the US, were denied coverage by the US insurance company because they filled in their birth date using the universal system rather than the US system of writing dates )

Answer 2

Thank you soo much for your help.

We lived in Winnipeg for 2 1/2 years.
It was a great experience, but gave us
a new respect for 30 degrees below zero
winters. Having come from the deep south it was a huge adjustment. Now living again in the deep south U.S. but enjoying our memorable experiences in Wpg.

Answer 3

I have been to Winnipeg only a few times, and only in the summer. Then the opposite was true, +35° C .

Living in the "balmy" southern part of Ontario we have not experienced -30 for several years now. Every new year seems to set a new record was "warmest winter on record".