Regular Expression to match a valid day in a date

Question

I need help coming up with a regex to make sure the user enters a valid date The string will be in the format of mm/dd/yyyy

Here is what I have come up

Answer 1

Regex for 0-31:

(0[1-9]|[12]\d|3[01])

Or if you don't want days with a preceding zero (e.g. 05):

([1-9]|[12]\d|3[01])

Answer 2

Regex for 0-31 day:

0[1-9]|[12]\d|3[01]) without prefix 0 - when "1", "23"...

([1-9]|[12]\d|3[01]) with prefix 0 - when "01", "04"

(0?[1-9]|[12]\d|3[01]) - with or without "0" - when ""

Answer 3

Simpler regex:

([12]\d|3[01]|0?[1-9])

Consider the accepted answer and this expression:

(0[1-9]|[12]\d|3[01])

This matches 01 but not 1

The other expression in the accepted answer:

([1-9]|[12]\d|3[01])

This matches 1 but not 01

It is not possible to add an OR clause to get them both working.

The one I suggested matches both. Hope this helps.

Answer 4

Is regular expression a must? If not, you better off using a different approach, such as DateTime::Format::DateManip

my @dates = (
    '04/23/2009',
    '01/22/2010 6pm',
    'adasdas',
    '1010101/12312312/1232132'
);

for my $date ( @dates ) 
{
    my $date = DateTime::Format::DateManip->parse_datetime( $date );
    die "Bad Date $date"  unless (defined $date);
    print "$dt\n";
}

Answer 5

Try it:
/(0?[1-9]|1[012])\/(0?[1-9]|[12][0-9]|3[01])\/((19|20)\d\d)/

Answer 6

This isn't all that hard...

qr#^
    (?: 0[1-9] | 1[012] )
    /
    (?:
        0[1-9] | 1[0-9] | 2[0-8]
        | (?<! 0[2469]/ | 11/ ) 31
        | (?<! 02/ ) 30
        | (?<! 02/
             (?= ... 
                 (?: 
                     .. (?: [02468][1235679] | [13579][01345789] )
                     | (?: [02468][1235679] | [13579][01345789] ) 00
                 )
             )
        ) 29
    )
    /
    [0-9]{4}
    \z
#x