if （h1 == ' 2'&& h2大于' 3'）

如果任何字符无效，此时此测试是多余的。它应该是初始 if 语句的一部分。类似于：

  if （（h1< '   0' || h1> '  2'）||（h2< '  0' || h2> '  9'）||（m1< '  0' || m1> '  5' ）||（m2< '  0' || m2> '  9'）||（h1 == '  2'&& h2> '  3' ））
 {
 printf（ 时间格式不是HH：MM。）; 
 return   1 ; 
} 

I want to check if the input is in the time format HH:MM. Valid time is from 00:00 to 23:59. I did:

printf("Please enter you age: ");
scanf("%f", &age);
if (age < 18) 
{
    printf("Too young, we can't serve you.\n");
    return 1;
}

printf("Please enter the time in the format HH:MM: ");
scanf("%c%c%c%c%c", &h1, &h2, &colon, &m1, &m2);
if ((h1 < '0' || h1 > '2') || (h2 < '0' || h2 > '9') || (m1 < '0' || m1 > '5') || (m2 < '0' || m2 > '9')) 
{
    if (h1 == '2' && h2 > '3')
    {
            printf("The time is not in the format HH:MM.");
            return 1;
    }
}

but it doesn't work.

if (h1 == '2' && h2 greater than '3')

If any character is invalid, this test is redundant at this point. It should be part of the initial if statement. Something like:

if ((h1 < '0' || h1 > '2') || (h2 < '0' || h2 > '9') || (m1 < '0' || m1 > '5') || (m2 < '0' || m2 > '9') || (h1 == '2' && h2 > '3'))
{
        printf("The time is not in the format HH:MM.");
        return 1;
}