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 mon

Answer 1

Maintainable Perl 5.10 version

/
  (?:
      (? (?&mon_29)) [\/] (?(?&day_29))
    | (? (?&mon_30)) [\/] (?(?&day_30))
    | (? (?&mon_31)) [\/] (?(?&day_31))
  )
  [\/]
  (? [0-9]{4})
  
  (?(DEFINE)
    (? 0?2 )
    (? 0?[469]   | (11) )
    (? 0?[13578] | 1[02] )

    (? 0?[1-9] | [1-2]?[0-9] )
    (? 0?[1-9] | [1-2]?[0-9] | 30 )
    (? 0?[1-9] | [1-2]?[0-9] | 3[01] )
  )
/x

You can retrieve the elements by name in this version.

say "Month=$+{month} Day=$+{day} Year=$+{year}";

( No attempt has been made to restrict the values for the year. )