正则表达式匹配日期和时间

Question

I'm trying to match a specific datetime format in PHP's regex:

dd-mm-YYYY HH:ii:ss

It should always be in that format. Meaning that for example when it is the first day of the month there must be a leading zero. Eg:

01-01-2013 01:01:01

I tried it with the following pattern:

^[0-12]{2}-[0-31]{2}-[0-9]{4} [0-23]{2}:[0-59]{2}:[0-59]{2}$

But the above pattern fails on timestamps like: 09-05-2013 19:45:10 .

http://rubular.com/r/eGBAhwiNCR

I understand this may not be the correct approach to validate a date time like this, but I really want to know what is wrong with the above.

Answer 1

[0-12]{2} matches not the numbers 0 till 12 . Instead it's a character class allowing 0 to 1 and also the number 2 . The subsequent quantifier just allows the repetition of those, meanding 0,1 or 2 repeated two times.

Your other placeholders follow the same non-functioning scheme.

It's best to resort to \\d{2} or \\d{4} if you can't google a better regex. Even better yet, just use DateTime to verify the format.

Answer 2

The problem is when you are checking the "ranges", for example [0-12] at the beginning. That is a character class, and it is telling the regex to match 0 through 1, and then 2. So if you added more numbers in after the 1st one, it isn't working as you are expecting. Changing your regex slightly (focused on the [0-12] initial), [0-319]{2}-[0-12]{2}-[0-9]{4} [0-23]{2}:[0-59]{2}:[0-59]{2}$ , would match 09-01-2011 11:11:10 .

Ensuring there are valid numbers for each of those spaces requires a little thinking outside the box. The regex:

(0[1-9]|[12][\\d]|3[0-2])-(0[1-9]|1[0-2])-[\\d]{4} (0[1-9]|1[\\d]|2[0-3]):(0[1-9]|[1-5][\\d]):(0[1-9]|[1-5][\\d])$

will work for what you are expecting with the regex you attempted .

If you break it down into smaller pieces it makes sense (it looks really scary at the beginning). Looking at the first piece (0-31 for "days").

(0[1-9]|[12][\\d]|3[0-2])

This is using an or to handle 3 different cases.

1. 0[1-9] - a zero followed by any number between 1-9. We don't want [0-9]{2} since that will allow numbers like 00 . So a number is valid if it starts with 0 and has any other number after it (for single digit days).
2. [12][\\d] - a 1 or 2 followed by any digit. This allows the numbers 10-29 to be valid.
3. 3[0-2] - a 3 followed by anything 0 through 2 matching 30 , 31 , and 32 .

Broken down, it's not too bad but this pattern is then carried out for each "field" in your date. So this regex validates on each field being valid... but a better way to confirm valid dates maybe needed. This doesn't get into the complexity of checking if you can have 30-02 for example, where February doesn't have 30 days.

Answer 3

^[0-9]{2}-[0-9]{2}-[0-9]{4} [0-9]{2}:[0-9]{2}:[0-9]{2}$

Answer 4

The example of validation is in php but the regex is standard

/*pass the date you wanna validate as parameter to the function.
The function returns true if it is valid and false if the date passed is not valid
*/   
function DateValid($date){
    //format will be fr if the date is in french format and en if the date is in en format
    $format='';
    //regex that tests if the date is in french format or english, if not in one of these two then it is not valid
    if(preg_match("#^(\d{1,2})[\-./ ](\d{1,2})[\-./ ](\d{4})(?: (\d{1,2})(?:[ .-](\d{1,2})){1,2})?$#",$date,$m)){
        $format='fr';
    }elseif (preg_match('#^(\d{4})[-. ](\d{1,2})[-. ](\d{1,2})(?: (\d{1,2})(?:[ .-](\d{1,2})){1,2})?$#', $date, $m)) {
        $format='en';
    }else{
         echo '<p style="font-size:150px">not english nor french</p>';
        return false;
    }
    //If it is french format or English then check if the date is correct
     if($format=='fr'){
         if (checkdate($m[2], $m[1], $m[3]) == false || $m[4] >= 24 || $m[5] >= 60 || $m[6] >= 60) {
            echo '<p style="font-size:150px">Not valid french</p>';
            return false;
        }else{
             echo '<p style="font-size:150px">Valid french</p>';
             return true;
        }
     }elseif($format=='en'){
         if (checkdate($m[2], $m[3], $m[1]) == false || $m[4] >= 24 || $m[5] >= 60 || $m[6] >= 60) {
             echo '<p style="font-size:150px">Not valid english</p>';
             return false;
        }else{
            echo '<p style="font-size:150px">Valid english</p>';
            return true;
        }
     }
}