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Date input validation (Regular Expressions) [2]

Posted on 2016-11-27
Medium Priority
Last Modified: 2016-11-27
I had this question after viewing Date input validation (Regular Expressions).

Hi guys,
I have expression below :

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1. Day validation of 28, 29, 30, 31
2. years in range 1800-2099
3. seperator /
4. format dd/mm/yyyy

I tied to fix days and months in range   1, 2, 3, 4, . . .  or  01, 02, 03, 04, . . .

validation is successful on any month and any year (include leap year)
Except these entries on February: 1/2/2016, 2/02/2016, 3/2/2017 . . .  Failure on one digit day.

 Thank you!
Question by:Darius
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LVL 19

Expert Comment

by:Kim Ryan
ID: 41903389
Looks like you just left out the ? after 0 day in February, line 6 in the Perl example below
my $a = '2/02/2016';

if ($a =~ /^
    ((0?[1-9]|[12][0-9]|3[01])[\/](0?[13578]|1[02])[\/](18|19|20)[0-9]{2})|  # jan, march, may etc
    ((0?[1-9]|[12][0-9]|30)[\/](0?[469]|11)[\/](18|19|20)[0-9]{2})|          # apr, jun etc
    ((0?[1-9]|1[0-9]|2[0-8])[\/](0?[2])[\/](18|19|20)[0-9]{2})|              # feb
    (29[\/](0?[2])[\/](((18|19|20)(04|08|[2468][048]|[13579][26]))|2000))$   # leap day
    /x )
    print "matched day: $1\n";

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There are plenty of lubraries to do this type of validation: Date::Parse

Author Comment

ID: 41903399
Hi Kim,

  I have the same changes done, but it brake February validation

For example:  29/2/2017,  29/02/2017,  29/2/2018,  29/02/2018, 29/2/2019,  29/02/2019, . . .

Leap year 2016, 2020, . . .  correct!

LVL 19

Accepted Solution

Kim Ryan earned 2000 total points
ID: 41903459
The anchors point ^ and $ didn't seem to be working, they need to be inside brackets.

    ((^0?[1-9]|[12][0-9]|3[01])[\/](0?[13578]|1[02])[\/](18|19|20)[0-9]{2})$|  # jan, march, may etc
    ((^0?[1-9]|[12][0-9]|30)[\/](0?[469]|11)[\/](18|19|20)[0-9]{2})$|          # apr, jun etc
    ((^0?[1-9]|1[0-9]|2[0-8])[\/](0?[2])[\/](18|19|20)[0-9]{2})$|              # feb
    $))   # leap day

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This would be a lot simpler if you just extracted dd, mm, yyyy and then used if then logic to validate all cases (such as is year divisible by 4 but not 400 etc).

Author Comment

ID: 41903468

This is just a challenge for myself. Thanks for help!

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