Regular Expression Match to test for a valid year

Question

Given a value I want to validate it to check if it is a valid year  My criteria is simple where the value should be an integer with 4 characters  I know this is not the best solution as it will not allow years before 1000 and will allow years such as 5000  This criteria is adequate for my current scenario   What I came up with is   d 4    While this works it also allows negative values   How do I ensure that only positive integers are allowed

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d 4    This will check if a string consists of only 4 numbers  In this scenario  to input a year 989  you can give 0989 instead

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To test a year in a string which contains other words along with the year you can use the following regex   b d 4  b

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I use this regex in Java   0 1-9  1 012      0 1-9   12  0-9  3 01      19  2-9  0-9   0-9  2    Works from 1900 to 9999

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Years from 1000 to 2999    12  0-9  3     For 1900-2099    19 20  d 2

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You could convert your integer into a string  As the minus sign will not match the digits  you will have no negative years

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You can also use this one      0-2  0-9  3 0-1      0-1  0-2     19 789  d 20 01  d

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In my case I wanted to match a string which ends with a year  4 digits  like this for example  Oct 2020 Nov 2020 Dec 2020 Jan 2021  It ll return true with this one  var sheetName    Jan 2021   var yearRegex   new RegExp  quot  b d 4   quot    var isMonthSheet   yearRegex test sheetName   Logger log  isMonthSheet       isMonthSheet    The code above is used in Apps Script  Here s the link to test the Regex above  https   regex101 com r SzYQLN 1

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Use     19  2-9  0-9   d 2      for years 1900 - 9999   No need to worry for 9999 and onwards - A I  will be doing all programming by then      Hehehehe  You can test your regex at https   regex101 com   Also more info about non-capturing groups   mentioned in one the comments above    here http   www manifold net doc radian why do non-capture groups exist  htm

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If you need to match YYYY or YYYYMMDD you can use                     1-9  d    0 48   2468  048   13579  26          2468  048   13579  26  00     0 2   29           1-9  d 3           0  13578  1 02     31         0  13-9  1 0-2     29 30         0  1-9      1 0-2      0  1-9  1 d 2 0-8          19 20  d 2

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you can go with sth like   -  d 4    you prevent the minus sign - to be before your 4 digits  you can also use   d 4   with   to catch the beginning of the string  It depends on your scenario actually

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The  accepted  answer to this question is both incorrect and myopic   It is incorrect in that it will match strings like 0001  which is not a valid year   It is myopic in that it will not match any values above 9999  Have we already forgotten the lessons of Y2K  Instead  use the regular expression     1-9  d 3      If you need to match years in the past  in addition to years in the future  you could use this regular expression to match any positive integer     1-9  d     Even if you don t expect dates from the past  you may want to use this regular expression anyway  just in case someone invents a time machine and wants to take your software back with them   Note  This regular expression will match all years  including those before the year 1  since they are typically represented with a BC designation instead of a negative integer  Of course  this convention could change over the next few millennia  so your best option is to match any integer   positive or negative   with the following regular expression    -  1-9  d

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This works for 1900 to 2099          19 20  0-9  2

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You need to add a start anchor   as     d 4     Your regex  d 4   will match strings that end with 4 digits  So input like -1234 will be accepted   By adding the start anchor you match only those strings that begin and end with 4 digits  which effectively means they must contain only 4 digits

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In theory the 4 digit option is right  But in practice it might be better to have 1900-2099 range   Additionally it need to be non-capturing group  Many comments and answers propose capturing grouping which is not proper IMHO  Because for matching it might work  but for extracting matches using regex it will extract 4 digit numbers and two digit  19 and 20  numbers also because of paranthesis   This will work for exact matching using non-capturing groups      19 20  d 2

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Building on  r92 answer  for years 1970-2019    19 789  d 20 01  d

[regex] Regular Expression Match to test for a valid year

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