Reputation: 101

Regular Expression for two-digit month and two-digit day only

I've been searching high and low for a regex that will validate MM/DD only. I do not need year (we're asking in a form for fiscal year ends, so we don't need a year, we need to know the range of their fiscal year).

For example, I need them to be able to enter 06/30 or 12/31 for Jun 30th or Dec 31st, respectively. All the regex examples I was able to find include the year as part of the date, which I do not need and I am very unfamiliar with regular expression syntax. What regex can I use for for two digit month and day only?

Upvotes: 4

Answers (5)

Geo

Reputation: 13006

The pattern you need is:

#(0[13578]|1[02])/(0[1-9]|[12][0-9]|3[01])|(0[469]|11)/(0[1-9]|[12][0-9]|30)|02/(0[1-9]|[12][0-9])#

Testing it in PHP:

<?

$p = '#' . implode('|', array(
    '(0[13578]|1[02])/(0[1-9]|[12][0-9]|3[01])', // 31-day months
    '(0[469]|11)/(0[1-9]|[12][0-9]|30)', // 30-day months
    '02/(0[1-9]|[12][0-9])', // February
)) . '#';

for ($m = 0; $m < 14; $m++) {
    for ($d = 0; $d < 33; $d++) {
        $date = sprintf('%02d/%02d', $m, $d);
        echo $date . ' - ' . preg_match($p, $date) . "\n";
    }
    echo "\n";
}

And the results are:

Upvotes: 3

Ed Heal

Reputation: 60007

For all months (i.e. 28 days):

(0[1-9]|1[0-2])/([01][1-9]|10|2[0-8])

For all months apart from February:

(0[13-9]|1[0-2])/(29|30)

For months with 31 days (i.e.01, 03, 05,07, 08, 10 and 12)

(0[13578]|1[0-2])/31

Putting this together

((0[1-9]|1[0-2])/([01][1-9]|10|2[0-8]))|((0[13-9]|1[0-2])/(29|30))|((0[13578]|1[0-2])/31)

Then for leap years append the following to the regular expression

|02/29

Upvotes: 12

Andrew Clark

Reputation: 208505

Regex is not the right answer for this, use a date library to perform this validation.

That being said, here is a regex that should do the trick (this should hopefully help to convince you that regex is not the right answer):

^(0[13578]|1[02])/([012]\d|3[01])|(0[469]|11)/([012]\d|30)|02/[012]\d$

If you just need simple validation that doesn't check for number of days in a month, you could use the following:

^(0[1-9]|1[012])/([012]\d|3[01])$

Upvotes: 0

Anirudha

Reputation: 32807

You can avoid regex and instead use method like split

So,you must follow these steps

1>Split the string with /

2>Parse the resulting MM and DD to an integer

3>now compare parsed integers to check whether it's a valid month or day..

Upvotes: 2

Matt Crouch

Reputation: 1738

I think this might work

^(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])$

Upvotes: 0

Regular Expression for two-digit month and two-digit day only

Answers (5)

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