Created Day of the Week calculator

C/day_of_the_week.c

@@ -0,0 +1,70 @@
+// Program to fetch day of the week for a given day
+
+#include <stdio.h>
+
+int isLeapYear(int year)
+{
+    if(year % 400 == 0)
+        return 1;
+    if(year%100 == 0)
+        return 0;
+    if(year%4 == 0)
+        return 1; 
+    return 0;
+}
+
+void calculateDay(int date, int month, int year)
+{
+    int century_digits = (int)(year / 100);
+    int year_digits = year % 100;
+    int value = year_digits + (int)(year_digits / 4);
+
+    if(century_digits == 18)
+        value += 2;
+    else if(century_digits == 20)
+        value += 6;
+
+    switch(month)
+    {
+        case 1: if(!isLeapYear(year))
+                    value += 1;
+                break;
+        case 2: if(isLeapYear(year))
+                    value += 3;
+                else
+                    value += 4;
+                break;
+        case 3: value += 4; break;
+        case 5: value += 2; break;
+        case 6: value += 5; break;
+        case 8: value += 3; break;
+        case 9: value += 6; break;
+        case 10: value += 1; break;
+        case 11: value += 4; break;
+        case 12: value += 6; break;
+    }
+
+    value = (value + date) % 7;
+
+    switch(value)
+    {
+        case 0: printf("SATURDAY"); break;
+        case 1: printf("SUNDAY"); break;
+        case 2: printf("MONDAY"); break;
+        case 3: printf("TUESDAY"); break;
+        case 4: printf("WEDNESDAY"); break;
+        case 5: printf("THURSDAY"); break;
+        case 6: printf("FRIDAY"); break;
+    }
+}
+
+int main()
+{
+    //Sample Date
+    int date = 20;
+    int month = 10;
+    int year = 2021;
+
+    calculateDay(date, month, year);
+    return 0;
+}