How to validate and parse date in C? - c

Question

I'm getting this date as invalid "006.010.002021" and my question is, how can I validate it and convert it to "06.10.2021"
thank you in advance
int isDateValid(sDate date)
{
int daysPerMonth;
switch (date.month)
{
case 1:
case 2:
daysPerMonth = 28;
break;
case 3:
case 4:
case 5:
case 6:
case 7:
case 8:
case 9:
case 10:
case 11:
daysPerMonth = 30;
break;
case 12:
daysPerMonth = 31;
break;
default:
return 0;
}
if ((daysPerMonth == 28) && isLeapYear(date.year))
daysPerMonth++;
if (date.day > daysPerMonth || date.day <= 0 || date.day > 2117 || date.year < 1917)
return 0;
}

Answer 1

You can use strptime() to read a string into a date/time format. However, you can only check if the string failed or not, it will not tell you what is wrong and how to fix it.
The best way to handle a wrong date is to throw an error informing the user that the date is wrong, because your code can not fix it.
Your case 1: will assign 28 days to january as well and the other cases will also yield wrong days per month.
switch (date.month)
{
case 2:
daysPerMonth = 28;
break;
case 4:
case 6:
case 9:
case 11:
daysPerMonth = 30;
break;
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
daysPerMonth = 31;
break;
default:
return 0;
}