one month calendar in c - c

Question

I'm trying to make a one-month calendar in C. This code kind of works, but for some inputs the spacing is off. I don't quite know how to fix it.
Also, if you have a way of making a one month calendar that involves less code than this, that would be great, since I have to regurgitate this on a test in about an hour.
Thanks!
int main() {
int spaces, days_in_month, day_of_week, i;
printf("Please enter the numier of days in the month:\n");
scanf("%d", &days_in_month);
printf("Please enter starting day of the week:\n");
scanf("%d", &day_of_week);
spaces = day_of_week - 1;
printf("Here's your calendar:\n");
for (i=0; i<spaces; i++)
printf(" ");
for (i=1; i<=(7-spaces); i++)
printf(" %d", i);
printf("\n");
if ((i-spaces) >10 && (i-spaces) < 14-spaces)
printf(" ");
for (i=(8-spaces); i<=(10-spaces); i++)
printf(" %d", i);
for (i=(11-spaces); i<=(14-spaces); i++)
printf(" %d", i);
printf("\n");
for (i=(15-spaces); i<=(21-spaces); i++)
printf(" %d", i);
printf("\n");
for (i=(22-spaces); i<=(28-spaces); i++)
printf(" %d", i);
printf("\n");
for (i=(29-spaces); i<=days_in_month; i++)
printf(" %d", i);
return 0;
}

Answer 1

Use %2d instead of %d so if a day has number 1...9 printf inserts a space for you.

Answer 2

How was your test?
Here is one simpler way to approach it (ignoring input validation):
// Normalize day of week to be 0-6 rather than 1-7.
day_of_week -= 1;
// Pad the first line of the calendar.
for(i = 0; i < day_of_week; i++)
printf(" ");
// For each day in the month...
for(i = 1; i <= days_in_month; i++)
{
// Print the date for the current day_of_week.
// '%3d' will print the value padding with spaces if necessary such that
// at least 3 characters are written.
printf("%3d", i);
// Increment the day_of_week.
// The modulo operator '% 7' will cause day_of_week to wrap around to 0
// when day_of_week reaches 7.
day_of_week = (day_of_week + 1) % 7;
// if the new day_of_week is 0, output a newline to start at the
// beginning of the next line.
if(day_of_week == 0)
printf("\n");
}
A sample run produces the following output:
$ ./calendar.exe
Please enter the numier of days in the month:
28
Please enter starting day of the week:
6
Here's your calendar:
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28

Answer 3

#include<stdio.h>
int main(void)
{
int start_day, days_in_month, i, day_of_week;
printf("Enter start day: ");
scanf("%d", &start_day);
printf("Enter days in month: ");
scanf("%d", &days_in_month);
for(i = 1 ; i < start_day; i++) {
printf(" ");
}
for(i = 1; i <= days_in_month; i++) {
printf("%2d ", i);
if((i + start_day - 1)%7 ==0) {
printf("\n");
}
}
return 0;
}