This C++ program shows the day of the week for a given date by taking in inputs for the century, date, and year. It uses a calculation method that factors in the century, month, and year to determine the day of the week as a number from 0-6, then prints out the corresponding day name. The program also has error handling to validate the numeric inputs are valid dates.

1. 1 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
Task 4:
//daycalculation.cpp
C++ program: shows the day of the
week by date given
Khalid Waleed
CANAL HIGH INSTITUTE OF ENGINEERING & TECHNOLOGY
Prepared By:

2. 2 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
1: // daycalculation.cpp
2: // shows the day of the week by date given
3: #include <iostream>
4: using namespace std;
5: void error(int &);
6: int main()
7: {
8: int day, month, m, year, century, day_of_week;
9: char ask;
10: cout <<" program to show the day of the week by date n";
11: cout <<"-------------------------------------------------------------"<<endl;
12: cout <<"centuries availiable : 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23";
13: cout <<"n ***** Note: we are now in the 21st century ***** n";
14: do
15: {
16: cout <<"please Enter the century number: ";
17: cin >> century;
18: error(century);
19: switch (century)
20: {
21: case 20:
23: break;
22: century;
24: case 21:
25: --century;
26: break;
27: case 19:
28: century+=2;
29: break;
30: case 18:

3. 3 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
31: century++;
32: break;
33: case 22:
34: century+=2;
35: break;
36: case 23:
37: century+=2;
38: break;
39: case 17:
40: century+=2;
41: break;
42: case 16:
43: century+=3;
44: break;
45: case 15:
46: century+=3;
47: break;
48: case 14:
49: century-=2;
50: break;
51: case 13:
52: century--;
53: break;
54: default:
55: cout <<"century number not in the list n";
56: cout <<"Day calculation may not be accurate n";
57: cout <<"do you want to continue (y/n) ?";
58: cin >> ask;
59: if(ask == 'y')
60: break;
61: else

4. 4 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
62: goto again;
63: }
64: cout <<"Enter the date (day/month/year) n";
65: cout <<"day number = "; cin >> day;
66: error(day);
67: if (day >31)
68: {
69: cout <<"Unknown day! n";
70: goto again;
71: }
72: cout <<"month number = "; cin >> month;
73: error(month);
74: switch(month)
75: {
76: case 1:
77: m =6;
78: break;
79: case 2:
80: m =2;
81: break;
82: case 3:
83: m =2;
84: break;
85: case 4:
86: m =5;
87: break;
88: case 5:
89: m =0;
90: break;
91: case 6:
92: m =3;

5. 5 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
93: break;
94: case 7:
95: m =5;
96: break;
97: case 8:
98: m =1;
99: break;
100: case 9:
101: m =4;
102: break;
103: case 10:
104: m =6;
105: break;
106: case 11:
107: m =2;
108: break;
109: case 12:
110: m =4;
111: break;
112: default:
113: cout <<"Unknown month! n";
114: goto again;
115: }
116: cout <<"year number = "; cin >> year;
117: error(year);
118: day_of_week =( day + m + year +(year/4)+ century )%7;
119: switch(day_of_week)
120: {
121: case 6:
122: cout <<"the day was a Saturday n";
123: break;

6. 6 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
124: case 0:
125: cout <<"the day was a Sunday n";
126: break;
127: case 1:
128: cout <<"the day was a Monday n";
129: break;
130: case 2:
131: cout <<"the day was a Tuesday n";
132: break;
133: case 3:
134: cout <<"the day was a Wednesday n";
135: break;
136: case 4:
137: cout <<"the day was a Thursday n";
138: break;
139: case 5:
140: cout <<"the day was a Friday n";
141: break;
142: default:
143: cout <<"ERROR!! n";
144: }
145: again:
146: cout <<"Do again (y/n)? : ";
147: cin >> ask;
148: }while(ask == 'y');
149: return 0;
150: }
151: void error(int &x)
152: {
153: while (cin.fail())
154: {

7. 7 | P a g e C A N A L H I G H E R I N S T I T U T E O F E N G I N E E R I N G & T E C H N O L O G Y
155: cin.clear();// clear input buffer to restore cin to a usable state
156: cin.ignore(INT_MAX, 'n');// ignore last input
157: cout <<"You can only enter numbers.n";
158: cout <<"Enter a number : ";
159: cin >> x;
160: }
161: }