For a better understanding, we always recommend you to learn the basic topics of C programming listed below:

In this c program, we need to change the number of days into the format of **years**, **weeks**, and **days**. That means if the user has input 372** **days, the output of the c program should be 1 year and 1 week like that. Here we need to convert the number of days into years and the remaining days into weeks and days.

In this c program, we use the **mod** operator to find the remainder of the year and week. First, we define the number of days in a week as **7**. After accepting the user input, for finding years, we divide the number of days by **365**. To calculate the remaining weeks, use mod the number with 365** **and divide that remainder with 7. Like that, we have to find out the days also. Step by step procedure that happens in this program is:

- 1. Input the number of variables and placed it in variable '
**n**' days. - 2. To get the number of Years, Divide the input by
**365**and store the Quotient as the Year. - 3. For calculating the number of Weeks, Divide input by
**365**, and obtain the Remainder. Divide the Remainder again by 7(number of days in a week) and store Quotient in variable '**week**'. - 4. To get the number of Days, Divide the input by
**365**and obtain the Remainder. Again Divide the Remainder with**7**(number of days in a week) and get the Remainder. Store the value in the variable**Days**. - 5. Print the Output and then Exit.

**#define**__ __is used to Declare the **constant **values in our program. Here we define the Constant **DAYINWEEK**; its value is 7. We can use the Constant '**DAYINWEEK**' in this example to calculate the Week, Days, etc.

The Syntax for defining a Constant is:

**#define ConstantName Value**

- 'ConstantName' is the name of the constant Variable.
- Value is the value of the Variable.

**STEP 1: **Include the Header files to use the built-in Functions in the C program.

**STEP 2:** Declare the variables '**ndays**, **Year**, **week**, **days**' as integer and Define **DAYSINWEEK 7**.'

**STEP 3:** Read the number of Days into '**ndays**'.

**STEP 4:** Calculate Year as '**ndays/365**'.

**STEP 5:** Calculate Week as '**(ndays % 365)/DAYSINWEEK**'.

**STEP 6:** Calculate Days as '**(ndays65) % DAYSINWEEK**'.

**STEP 7:** Display '**ndays**' is equivalent to '**year**' and '**week**' and '**days**' using the `printf`

function.

` ````
#include <stdio.h>
#define DAYSINWEEK 7
void main()
{
int ndays, year, week, days;
printf("Enter the number of days\n");
scanf("%d", & ndays);
year = ndays / 365;
week = (ndays % 365) / DAYSINWEEK; /* calculating the years, weeks and days */
days = (ndays% 365) % DAYSINWEEK;
printf("%d is equivalent to %d years, %d weeks and %d days\n", ndays, year, week, days);
}
```

Enter the number of days 375 375 is equivalent to 1 year, 1 week and 3 days Enter the number of days 423 423 is equivalent to 1 year, 8 weeks, and 2 days Enter the number of days 1497 1497 is equivalent to 4 years, 5 weeks and 2 days