1 files changed, 28 insertions, 2 deletions

diff --git a/5/8.c b/5/8.c
index a659364..f1bbc7f 100644
--- a/5/8.c
+++ b/5/8.c
@@ -6,8 +6,6 @@ int day_of_year(int year, int month, int day);
 /* Sets month and day from day of year */
 void month_day(int year, int yearday, int *pmonth, int *pday);
 
-int main() { return 0; }
-
 static char daytab[2][13] = {
     {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
     {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}};
@@ -15,6 +13,22 @@ static char daytab[2][13] = {
 int day_of_year(int year, int month, int day) {
   int i, leap;
 
+  // leap year logic is only valid if this is true.
+  if (year < 1752) {
+    printf("error: invalid year\n");
+    return -1;
+  }
+
+  if (month < 1 || month > 12) {
+    printf("error: invalid month\n");
+    return -1;
+  }
+
+  if (day < 1) {
+    printf("error: invalid day\n");
+    return -1;
+  }
+
   leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
 
   for (i = 1; i < month; i++)
@@ -25,6 +39,18 @@ int day_of_year(int year, int month, int day) {
 
 void month_day(int year, int yearday, int *pmonth, int *pday) {
   int i, leap;
+  
+  if (year < 0) {
+    *pmonth = *pday = 0;
+    printf("error: invalid year\n");
+    return;
+  }
+
+  if (yearday < 1) {
+    *pmonth = *pday = 0;
+    printf("error: invalid yearday\n");
+    return;
+  }
 
   leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;