Chapter 5, Problem 60PS

Write a program that, given a person's birth date (or any other date in the Gregorian calendar), will display the day of the week the person was born.

To determine the day of the week, you will first need to calculate the day of the week for December 31 of the previous year. To calculate the day for December 31, use the following formula.

$\left(\left(\text{year}-1\right)\times 365+\left[\frac{\text{year}-1}{4}\right]-\left[\frac{\text{year}-1}{100}\right]+\left[\frac{\text{year}-1}{400}\right]\right)\%7$

The formula determines the day based on the values as shown below.

$\begin{array}{l}\begin{array}{l}\text{Day 0: Sunday}\hfill \\ \text{Day 1: Monday}\hfill \\ \text{Day 2: Tuesday}\hfill \\ \text{Day 3: Wednesday}\hfill \\ \text{Day 4: Thursday}\hfill \\ \text{Day 5: Friday}\hfill \end{array}\\ \text{Day 6: Saturday}\end{array}$

Once you know the day for December 31, you simply calculate the days in the year before the month in question. Use a switch statement to make this calculation. If the desired month is 12, add the number of days for November (30). If it is 11, add the number of days for October (31). If it is 3, add the number of days for February (28). If it is 2, add the number of days for January (31). If you do not use a break between the months, the switch will add the days in each month before the current month.

To this figure, add the day in the current month and then add the result to the day code for December 31. This number modulo seven is the day of the week.

There is one more refinement. If the current year is a leap year, and if the desired date is after February, you need to add 1 to the day code. The following formula can be used to determine if the year is a leap year.

$\left(\text{!}\left(\text{year}\%\text{4}\right)\text{ \&\& }\left(\text{year}\%\text{100}\right)\right)\text{ |}\text{| !}\left(\text{year}\%\text{400}\right)$

Your program should have a function to get data from the user, another to calculate the day of the week, and a third to print the result.

To test your program, run it with the following dates:

$\begin{array}{l}\begin{array}{l}\text{a}\text{. February 28, 1900, and March 1, 1900}\hfill \\ \text{b}\text{. February 28, 1955, and March 1, 1955}\hfill \\ \text{c}\text{. February 28, 1996, and March 1, 1996}\hfill \\ \text{d}\text{. February 28, 2000, and March 1, 2000}\hfill \\ \text{e}\text{. December 31, 1996}\hfill \end{array}\\ \text{f}\text{. The first and last dates of the current week}\end{array}$ .