The World Almanac features a "perpetual calendar", a collection of possible calendars for every conceivable year. Find the lowest number of the calendars.
A)10 calendars
B) 28 calendars
C) 21 calendars
D) 14 calendars
E) 30 calendars

Question

The World Almanac features a "perpetual calendar", a collection of possible calendars for every conceivable year. Find the lowest number of the calendars. ​
A)10 calendars
B) 28 calendars
C) 21 calendars
D) 14 calendars
E) 30 calendars

Quizplus · Accepted Answer

The lowest number of calendars is achieved by finding the minimum number of different patterns that can represent every possible combination of days for each month. This can be done using what is known as the "Doomsday algorithm". The algorithm relies on 14 different calendars, which correspond to the 14 different possible ways that the Doomsday falls on the days of the week for a given year. Therefore, the lowest number of calendars is 14, which is option D.

The World Almanac Features a "Perpetual Calendar", a Collection of Possible