How To Validate Date With Regular Expression

How To Validate Date With Regular Expression

Date Format (dd/mm/yyyy hh:mm:ss) Regular Expression Pattern

(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d) ([01][0-9]|2[0-3]):([012345][0-9]):([012345][0-9])

Description:

    (          #start of group #1
     0?[1-9]  #  01-09 or 1-9
     |                  #  ..or
     [12][0-9]  #  10-19 or 20-29
     |   #  ..or
     3[01]  #  30, 31
    )    #end of group #1
     /   #  follow by a "/"
    (   #    start of group #2
    0?[1-9]  # 01-09 or 1-9
    |   # ..or
    1[012]  # 10,11,12
    )   #    end of group #2
    /   # follow by a "/"
    (   #   start of group #3
     (19|20)\\d\\d #     19[0-9][0-9] or 20[0-9][0-9]
     )          #   end of group #3

   #  follow by a " "
   (   #    start of group #4
    [01][0-9]  # 01-19
    |   # ..or
    2[0-3]  # 20-23
    )
 :  #  follow by a ":"
   (   #    start of group #5
    [012345][0-9] # 01-59
   )
 :  #  follow by a ":"
   (   #    start of group #6
     [012345][0-9] # 01-59
    )

The above regular expression is used to validate the date format in “dd/mm/yyyy”, you can easy customize to suit your need. However, it’s a bit hard to validate the leap year , 30 or 31 days of a month, we may need basic logic as below.

package com.javanotes2all.java.date;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class DateValidator{
 
  private Pattern pattern;
  private Matcher matcher;
 
  private static final String DATETIME_PATTERN ="((19|20)\\d\\d)-(0?[1-9]|1[012])-(0?[1-9]|[12][0-9]|3[01]) ([01][0-9]|2[0-3]):([012345][0-9]):([012345][0-9])";
 
  public DateValidator(){
   pattern = Pattern.compile(DATETIME_PATTERN);
  }

   public boolean validate(final String date){
 
     matcher = pattern.matcher(date);
 
     if(matcher.matches()){
 
  matcher.reset();
 
  if(matcher.find()){
 
             String day = matcher.group(1);
      String month = matcher.group(2);
      int year = Integer.parseInt(matcher.group(3));
 
      if (day.equals("31") && 
    (month.equals("4") || month .equals("6") || month.equals("9") ||
                  month.equals("11") || month.equals("04") || month .equals("06") ||
                  month.equals("09"))) {
   return false; // only 1,3,5,7,8,10,12 has 31 days
      } else if (month.equals("2") || month.equals("02")) {
                  //leap year
    if(year % 4==0){
     if(day.equals("30") || day.equals("31")){
      return false;
     }else{
      return true;
     }
    }else{
           if(day.equals("29")||day.equals("30")||day.equals("31")){
      return false;
           }else{
      return true;
     }
    }
       }else{     
  return true;     
       }
    }else{
           return false;
    }    
     }else{
   return false;
     }       
   }
}

use above code to validate like

new DateValidator().validate("31/06/2013 23:59:01");