Regular Expression to match valid dates

Question

I m trying to write a regular expression that validates a date   The regex needs to match the following   M D YYYY MM DD YYYY Single digit months can start with a leading zero  eg  03 12 2008  Single digit days can start with a leading zero  eg  3 02 2008  CANNOT include February 30 or February 31  eg  2 31 2008    So far I have       1-9  1 012   -     1-9   12  0-9  3 01   -    19 20  d d    1 012  0 1-9   3 01  2 d 1 d 0 1-9   19 20  d d    1 012  0 1-9   -    3 01  2 d 1 d 0 1-9   -    19 20  d d     This matches properly EXCEPT it still includes 2 30 2008  amp  2 31 2008   Does anyone have a better suggestion   Edit  I found the answer on RegExLib       0 13578     13578    1 02          1-9     0-2  0-9    3 01        0 469     469    11         1-9     0-2  0-9    30      2 02        1-9     0-2  0-9          d 4     d 4     It matches all valid months that follow the MM DD YYYY format   Thanks everyone for the help

User · Answer

To control a date validity under the following format :

YYYY/MM/DD or YYYY-MM-DD

I would recommand you tu use the following regular expression :

(((19|20)([2468][048]|[13579][26]|0[48])|2000)[/-]02[/-]29|((19|20)[0-9]{2}[/-](0[4678]|1[02])[/-](0[1-9]|[12][0-9]|30)|(19|20)[0-9]{2}[/-](0[1359]|11)[/-](0[1-9]|[12][0-9]|3[01])|(19|20)[0-9]{2}[/-]02[/-](0[1-9]|1[0-9]|2[0-8])))

Matches

2016-02-29 | 2012-04-30 | 2019/09/31

Non-Matches

2016-02-30 | 2012-04-31 | 2019/09/35

You can customise it if you wants to allow only '/' or '-' separators. This RegEx strictly controls the validity of the date and verify 28,30 and 31 days months, even leap years with 29/02 month.

Try it, it works very well and prevent your code from lot of bugs !

FYI : I made a variant for the SQL datetime. You'll find it there (look for my name) : Regular Expression to validate a timestamp

Feedback are welcomed :)

User · Answer

var dtRegex   new RegExp   1-9 -  4  0-9 -  2  0-9 -  2         if dtRegex test date     true           var evalDate   date split  -            if evalDate 0      0000   amp  amp  evalDate 1      00   amp  amp  evalDate 2      00                return true

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A slightly different approach that may or may not be useful for you   I m in php   The project this relates to will never have a date prior to the 1st of January 2008   So  I take the  date  inputed and use strtotime     If the answer is    1199167200 then I have a date that is useful to me   If something that doesn t look like a date is entered -1 is returned   If null is entered it does return today s date number so you do need a check for a non-null entry first   Works for my situation  perhaps yours too

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Here is the Reg ex that matches all valid dates including leap years  Formats accepted mm dd yyyy or mm-dd-yyyy or mm dd yyyy format            0  13578  1 02      -    31  1       0  1 3-9  1 0-2      -       29 30  2        1 6-9   2-9  d   d 2        0 2    -    29 3         1 6-9   2-9  d     0 48   2468  048   13579  26         16  2468  048   3579  26  00             0  1-9      1 0-2       -       0  1-9  1 d 2 0-8   4      1 6-9   2-9  d   d 2     courtesy Asiq Ahamed

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This is not an appropriate use of regular expressions  You d be better off using   0-9  2   0-9  2   0-9  4    and then checking ranges in a higher-level language

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I know this does not answer your question  but why don t you use a date handling routine to check if it s a valid date  Even if you modify the regexp with a negative lookahead assertion like    31 0 2   ie  do not match 31 2 or 31 02  you ll still have the problem of accepting 29 02 on non leap years and about a single separator date format    The problem is not easy if you want to really validate a date  check this forum thread    For an example or a better way  in C   check this link  If you are using another platform language  let us know

User · Answer

Sounds like you re overextending regex for this purpose  What I would do is use a regex to match a few date formats and then use a separate function to validate the values of the date fields so extracted

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Maintainable Perl 5 10 version                  lt month gt     amp mon 29           lt day gt    amp day 29            lt month gt     amp mon 30           lt day gt    amp day 30            lt month gt     amp mon 31           lt day gt    amp day 31                   lt year gt   0-9  4           DEFINE         lt mon 29 gt  0 2          lt mon 30 gt  0  469       11           lt mon 31 gt  0  13578    1 02            lt day 29 gt  0  1-9     1-2   0-9           lt day 30 gt  0  1-9     1-2   0-9    30          lt day 31 gt  0  1-9     1-2   0-9    3 01         x  You can retrieve the elements by name in this version  say  quot Month    month  Day    day  Year    year  quot      No attempt has been made to restrict the values for the year

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This regex validates dates between 01-01-2000 and 12-31-2099 with matching separators     0 1-9  1 012    -      0 1-9   12  0-9  3 01   2 19 20  d d

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if you didn t get those above suggestions working  I use this  as it gets any date I ran this expression through 50 links  and it got all the dates on each page     20 d d- Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec - 0 1-9   1-2  0-9  3 01

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If you re going to insist on doing this with a regular expression  I d recommend something like      0 1 0 3   lt     gt   10 11 12     0 1   lt     gt   30 31      0 2    0 1   lt     gt   28 29        19 20  0-9  2    This might make it possible to read and understand

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Regex was not meant to validate number ranges this number must be from 1 to 5 when the number preceding it happens to be a 2 and the number preceding that happens to be below 6   Just look for the pattern of placement of numbers in regex  If you need to validate is qualities of a date  put it in a date object js c  vb  and interogate the numbers there

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I landed here because the title of this question is broad and I was looking for a regex that I could use to match on a specific date format  like the OP   But I then discovered  as many of the answers and comments have comprehensively highlighted  there are many pitfalls that make constructing an effective pattern very tricky when extracting dates that are mixed-in with poor quality or non-structured source data    In my exploration of the issues  I have come up with a system that enables you to build a regular expression by arranging together four simpler sub-expressions that match on the delimiter  and valid ranges for the year  month and day fields in the order you require    These are  -  Delimeters     w d r n      This will match anything that is not a word character  digit character  carriage return  new line or colon  The colon has to be there to prevent matching on times that look like dates  see my test Data    You can optimise this part of the pattern to speed up matching  but this is a good foundation that detects most valid delimiters     Note however  It will match a string with mixed delimiters like this 2 12-73 that may not actually be a valid date    Year Values    d 4   d 2     This matches a group of two or 4 digits  in most cases this is acceptable  but if you re dealing with data from the years 0-999 or beyond 9999 you need to decide how to handle that because in most cases a 1  3 or  4 digit year is garbage   Month Values   0  1-9  1 0-2     Matches any number between 1 and 12 with or without a leading zero - note  0 and 00 is not matched   Date Values   0  1-9   12  d 30 31    Matches any number between 1 and 31 with or without a leading zero - note  0 and 00 is not matched   This expression matches Date  Month  Year formatted dates   0  1-9   12  d 30 31    w d r n   0  1-9  1 0-2     w d r n    d 4   d 2     But it will also match some of the Year  Month Date ones  It should also be bookended with the boundary operators to ensure the whole date string is selected and prevent valid sub-dates being extracted from data that is not well-formed i e  without boundary tags 20 12 194 matches as 20 12 19 and 101 12 1974 matches as 01 12 1974   Compare the results of the next expression to the one above with the test data in the nonsense section  below    b 0  1-9   12  d 30 31    w d r n   0  1-9  1 0-2     w d r n    d 4   d 2   b   There s no validation in this regex so a well-formed but invalid date such as 31 02 2001 would be matched  That is a data quality issue  and as others have said  your regex shouldn t need to validate the data    Because you  as a developer  can t guarantee the quality of the source data you do need to perform and handle additional validation in your code  if you try to match and validate the data in the RegEx it gets very messy and becomes difficult to support without very concise documentation   Garbage in  garbage out   Having said that  if you do have mixed formats where the date values vary  and you have to extract as much as you can  You can combine a couple of expressions together like so   This  disastrous  expression matches DMY and YMD dates     b 0  1-9   12  d 30 31    w d r n   0  1-9  1 0-2     w d r n    d 4   d 2   b    b 0  1-9  1 0-2     w d r n   0  1-9   12  d 30 31    w d r n    d 4   d 2   b    BUT you won t be able to tell if dates like 6 9 1973 are the 6th of September or the 9th of June  I m struggling to think of a scenario where that is not going to cause a problem somewhere down the line  it s bad practice and you shouldn t have to deal with it like that - find the data owner and hit them with the governance hammer   Finally  if you want to match a YYYYMMDD string with no delimiters you can take some of the uncertainty out and the expression looks like this   b  d 4   0 1-9  1 0-2   0 1-9   12  d 30 31  b   But note again  it will match on well-formed but invalid values like 20010231  31th Feb       Test data  In experimenting with the solutions in this thread I ended up with a test data set that includes a variety of valid and non-valid dates and some tricky situations where you may or may not want to match i e  Times that could match as dates and dates on multiple lines    I hope this is useful to someone   Valid Dates in various formats  Day  month  year 2 11 73 02 11 1973 2 1 73 02 01 73 31 1 1973 02 1 1973 31 1 2011 31-1-2001 29 2 1973 29 02 1976  03 06 2010 12 6 90  month  day  year 02 24 1975  06 19 66  03 31 1991 2 29 2003 02-29-55 03-13-55 03-13-1955 12 24 1974 12 30 1974 1 31 1974 03 31 2001 01 21 2001 12 13 2001  Match both DMY and MDY 12 12 1978 6 6 78 06 6 1978 6 06 1978  using whitespace as a delimiter  13 11 2001 11 13 2001 11 13 01  13 11 01 1 1 01 1 1 2001  Year Month Day order 76 02 02 1976 02 29 1976 2 13 76 09 31  YYYYMMDD sortable format 19741213 19750101  Valid dates before Epoch 12 1 10 12 01 660 12 01 00 12 01 0000  Valid date after 2038  01 01 2039 01 01 39  Valid date beyond the year 9999  01 01 10000  Dates with leading or trailing characters  12 31 21  31 12 1921AD 31 12 1921 10 55 12 10 2016  8 26 00 39 wfuwdf12 11 74iuhwf fwefew13 11 1974 01 12 1974vdwdfwe 01 01 99werwer 12321301 01 99  Times that look like dates  12 13 56 13 12 01 1 12 01PM 1 12 01 AM  Dates that runs across two lines  1 12 19 74  01 12 19 74 13 1946  31 12 20 08 13  Invalid  corrupted or nonsense dates  0 1 2001 1 0 2001 00 01 2100 01 0 2001 0101 2001 01 131 2001 31 31 2001 101 12 1974 56 56 56 00 00 0000 0 0 1999 12 01 0 12 10 -100 74 2 29 12 32 45 20 12 194  2 12-73

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Perl expanded version Note use of  x modifier                          31 day months              0 13578                 13578                1 02                                                  1-9                 0-2  0-9                3 01                                         30 day months              0 469                 469                11                                                 1-9                 0-2  0-9                30                              29 day month  Feb           2 02                                       1-9                 0-2  0-9                                          year      d 4            d 4     year only  x  Original      0 13578     13578    1 02          1-9     0-2  0-9    3 01        0 469     469    11         1-9     0-2  0-9    30      2 02        1-9     0-2  0-9          d 4     d 4

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Perl 6 version    rx           lt month gt      d    1  2        lt month gt   lt   12 or fail               lt day gt      d    1  2          given     lt month gt           when 1 3 5 7 8 10 12             lt day gt   lt   31 or fail               when 4 6 9 11             lt day gt   lt   30 or fail               when 2             lt day gt   lt   29 or fail               default   fail                         lt year gt      d    4           After you use this to check the input the values are available in    or individually as   lt month gt     lt day gt     lt year gt     those are just syntax for accessing values in       No attempt has been made to check the year  or that it doesn t match the 29th of Feburary on non leap years

[regex] Regular Expression to match valid dates

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