Regex matching a date and time - php

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. E.g.:
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.
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).
[12][\d] - a 1 or 2 followed by any digit. This allows the numbers 10-29 to be valid.
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;
}
}
}