Trying to improve regex for date validation

Question

I wrote a regex for validating date in the format MonthName dd, yyyy

The code below works for the date with 2 day digits:

^(January|February|March|April|May|June|July|August|September|October|November|December)\s+\d\d[,]\s+(19|20)\d\d

For date with one digit for day (ex: April 5, 2015) I use:

^(January|February|March|April|May|June|July|August|September|October|November|December)\s+\d[,]\s+(19|20)\d\d

How can I change my regex into a single regex for both options? (April 24, 2015 and April 5, 2015)

You shouldn't be parsing dates with regex... – Nir Alfasi Apr 24 '15 at 17:07 — Nir Alfasi, Apr 24 '15 at 17:07

score 6 · Accepted Answer · edited May 23 '17 at 10:24

6

The simplest way in line with your code: you just say it should be one or two digits. We can give the character count inside curly braces.

\s+\d{1,2}[,]\s+(19|20)\d{2}

Or more elaborate one as in this answer

edited May 23 '17 at 10:24

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answered Apr 24 '15 at 17:01

lanenok

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Pedro Lobito · Answer 2 · 2015-04-24T17:27:36.443

Your complete regex may look like this:

/^(January|February|March|April|May|June|July|August|September|October|November|December)\s+(\d{1,2}),?\s+((?:19|20)\d{2})$/i

Will match:

February 2 1976
August 11 2011
november 19 1966
march 11, 1945

Demo

Regex Explanation:

/^(January|February|March|April|May|June|July|August|September|October|November|December)\s+(\d{1,2}),?\s+((?:19|20)\d{2})$/gmi

i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])

^ assert position at start of a line
1st Capturing group (January|February|March|April|May|June|July|August|September|October|November|December)
    1st Alternative: January
        January matches the characters January literally (case insensitive)
    2nd Alternative: February
        February matches the characters February literally (case insensitive)
    3rd Alternative: March
        March matches the characters March literally (case insensitive)
    4th Alternative: April
        April matches the characters April literally (case insensitive)
    5th Alternative: May
        May matches the characters May literally (case insensitive)
    6th Alternative: June
        June matches the characters June literally (case insensitive)
    7th Alternative: July
        July matches the characters July literally (case insensitive)
    8th Alternative: August
        August matches the characters August literally (case insensitive)
    9th Alternative: September
        September matches the characters September literally (case insensitive)
    10th Alternative: October
        October matches the characters October literally (case insensitive)
    11th Alternative: November
        November matches the characters November literally (case insensitive)
    12th Alternative: December
        December matches the characters December literally (case insensitive)
\s+ match any white space character [\r\n\t\f ]
    Quantifier: + Between one and unlimited times, as many times as possible, giving back as needed [greedy]
2nd Capturing group (\d{1,2})
    \d{1,2} match a digit [0-9]
        Quantifier: {1,2} Between 1 and 2 times, as many times as possible, giving back as needed [greedy]
,? matches the character , literally
    Quantifier: ? Between zero and one time, as many times as possible, giving back as needed [greedy]
\s+ match any white space character [\r\n\t\f ]
    Quantifier: + Between one and unlimited times, as many times as possible, giving back as needed [greedy]
3rd Capturing group ((?:19|20)\d{2})
    (?:19|20) Non-capturing group
        1st Alternative: 19
            19 matches the characters 19 literally
        2nd Alternative: 20
            20 matches the characters 20 literally
    \d{2} match a digit [0-9]
        Quantifier: {2} Exactly 2 times
$ assert position at end of a line

Will it also match February 2, 1976 and August 11, 2011? And also is there a way to make month name case insensitive? Thank you — Coding Duchess, Apr 24 '15 at 17:24
it's just adding `/i` at the end. Which Language are you using ? I'll update my answer to make it case insensitive. — Pedro Lobito, Apr 24 '15 at 17:25
to match `,` you'll need to make the comma optional with `,?` — Pedro Lobito, Apr 24 '15 at 17:29
I'll updated one more time, if possible, next time please specify everything on your question, it's easier for both. — Pedro Lobito, Apr 24 '15 at 17:30
Please check it out, If my question helped you, please consider accepting it as the correct answer. Tks ! — Pedro Lobito, Apr 24 '15 at 17:32

Trying to improve regex for date validation

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