what will be the regular expression of date format like '01-Aug-12'.

I have the date format of dd-M-y in asp application and want to validate it from asp regular expression validator control.

what will be the regular expression of date format like '01-Aug-12'.

I have the date format of dd-M-y in asp application and want to validate it from asp regular expression validator control.

• javascript
• asp
• regex

• Have you read "regular expressions 101"? – zerkms Commented Aug 24, 2012 at 11:16
• Your date format does not match your example. Do you mean dd-MMM-yy as date format? – Sjoerd Commented Aug 24, 2012 at 11:19
• @Talha: it is any article about regex basics – zerkms Commented Aug 24, 2012 at 11:19
• are ok with using asp validation controls? – codeandcloud Commented Aug 24, 2012 at 12:06

6 Answers 6

A very basic format check would be:

\d{2}-[A-Za-z]{3}-\d{2} 

See for yourself here.

To actually validate, we need a day check like @Brijesh Gandhi suggested and then add a plete month list like this:

([12]\d|0[1-9]|3[0-1])-(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)-\d{2}

If you want to allow for lowercase months like aug, you can add the case-insensivity modifier ?i: like this...

([12]\d|0[1-9]|3[0-1])-(?i:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)-\d{2}

...but that will also allow a month like e.g. aUg - it might be most correct to only allow the first character to be upper- or lowercase.

([12]\d|0[1-9]|3[0-1])-([Jj]an|[Ff]eb|[Mn]ar|[Aa]pr|[Mm]ay|[Jj]un|[Jj]ul|[Aa]ug|[Ss]ep|[Oo]ct|[Nn]ov|[Dd]ec)-\d{2}

See this final version in action here.

Please note that this still will not detect invalid dates like 30-Feb-12. A regexp not accepting those special dates will be very long/ugly. Even using Javascript's Date.parse(...)/new Date(...) will not help detect those as it happily accepts the above mentioned, non-existant date, and return the 1st of March. So to be 100% correct, you need to either do plex coding yourself, or use a library like datejs.

Edit 1: Shortened @Brijesh Gandhi's day check a bit, updated Regexr link.

Edit 2: Remark on correctness.

Why regexp? I would validate it using

DateTime.TryParse(...)

Anyway a basic form of regex could be

[0-3][0-9]-[A-Z][a-z][a-z]-[0-9][0-9]

which could be better than nothing.

This won't be too elegant, but if you want to use regex to validate dates, it is here:

The regex with explanation

(
  (
    31-(Jan|Mar|May|Jul|Aug|Oct|Dec)|                                   # months with 31 days
    (0[1-9]|[12]\d|30)-(Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)|   # months with 30 or 31 days
    (0[1-9]|1\d|2[0-8])-Feb                                             # February up to 28th
  )
  -\d\d                                                                 # any two digits represent the year
)|
(
    29-Feb-([02468][048]|[13579][26])                                   # February 29th
)

This regex doesn't accept invalid dates like 00-Aug-00, 32-Aug-00 and 29-Feb-01 while accepting valid dates including leap days (29-Feb-04). Note that we assume 00 stands for year 2000, not 1900. So, we accepted 29-Feb-00 as leap day!

In one line:

See it in action:

((31-(Jan|Mar|May|Jul|Aug|Oct|Dec)|(0[1-9]|[12]\d|30)-(Jan|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)|(0[1-9]|1\d|2[0-8])-Feb)-\d\d)|(29-Feb-([02468][048]|[13579][26]))

Case-insensitivity

In Javascript, add an i as second parameter:

var re = new RegExp(regexStr, "i");

In ASP.NET, use RegexOptions.IgnoreCase:

Regex re = new Regex(regexStr,RegexOptions.IgnoreCase);

Regular Expression is definitely not the way to go here. We could do a simple Date.Parse which returns NaN if the date is not valid.

var myDate = '01-Aug-12​';
var isValidDate = !isNaN( Date.parse( myDate ));

try this regex

([1-2][0-9]|[0][1-9]|[3][0-1])-[a-zA-Z][A-Za-z][a-zA-Z]-[0-9][0-9]

00-aug-12 is not valid date according this regex [0-3][0-9]-[A-Z][a-z][a-z]-[0-9][0-9]

Here is regex for every bination of the date format dd-MMM-yy:

[0123][0-9]-[JFMASOND][aepuco][nbrylgptvc]-[0-9][0-9]

Note how the month part is overly strict, while you may still be able to supply an invalid date. Maybe it is better to try to parse the date and check whether it is valid.