How to Validate String Date Format in Java

Validating date String in Java can be tricky as you may not know which date format you are dealing with, so the best way can be to create a list of date formats that you support and iterate through it.

List of Some Valid Date Formats:

• yyyy-MM-dd
• MM/dd/yyyy
• dd-MM-yyyy
• yyyy/MM/dd
• MMMM dd, yyyy
• dd MMM yyyy
• yyyy-MM-dd HH:mm:ss
• MM/dd/yyyy HH:mm:ss
• dd-MM-yyyy HH:mm:ss
• yyyy/MM/dd HH:mm:ss
• MMMM dd, yyyy HH:mm:ss
• dd MMM yyyy HH:mm:ss
• EEE, d MMM yyyy HH:mm:ss Z
• yyyy-MM-dd'T'HH:mm:ss
• MM/dd/yyyy'T'HH:mm:ss
• dd-MM-yyyy'T'HH:mm:ss
• yyyy/MM/dd'T'HH:mm:ss
• MMMM dd, yyyy'T'HH:mm:ss
• dd MMM yyyy'T'HH:mm:ss
• EEE, d MMM yyyy'T'HH:mm:ss Z
• yyyy-MM-dd'T'HH:mm:ss.SSS
• MM/dd/yyyy'T'HH:mm:ss.SSS
• dd-MM-yyyy'T'HH:mm:ss.SSS
• yyyy/MM/dd'T'HH:mm:ss.SSS
• MMMM dd, yyyy'T'HH:mm:ss.SSS
• dd MMM yyyy'T'HH:mm:ss.SSS
• EEE, d MMM yyyy'T'HH:mm:ss.SSS Z
• yyyy-MM-dd'T'HH:mm:ss.SSSSSS
• MM/dd/yyyy'T'HH:mm:ss.SSSSSS
• dd-MM-yyyy'T'HH:mm:ss.SSSSSS

Example: Java 7 or before

package org.code2care.examples;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class ValidateDateExample {

    public static void main(String[] args) {

        String dateStr = "2023-12-25";

        //Add your valid date format list here
        String[] validFormats = {
            "yyyy-MM-dd",
            "MM/dd/yyyy",
            "dd-MM-yyyy",
            "yyyy/MM/dd",
            "MMMM dd, yyyy",
            "dd MMM yyyy"
        };

        if (isValidDateFormat(dateStr, validFormats)) {
            System.out.println("Date format is valid.");
        } else {
            System.out.println("Date format is not valid.");
        }
    }

    public static boolean isValidDateFormat(String dateStr, String[] validFormats) {
        for (String format : validFormats) {
            SimpleDateFormat sdf = new SimpleDateFormat(format);
            sdf.setLenient(false);

            try {
                Date date = sdf.parse(dateStr);
                if (date != null) {
                    return true;
                }
            } catch (ParseException e) {
                // Parsing failed, try the next format
            }
        }

        // None of the formats resulted in a valid date
        return false;
    }
}

Example: Java 8 or above

package org.code2care.examples;

import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.Arrays;

public class ValidateDateFormat {
    public static void main(String[] args) {
        String dateStr = "2023-July-25";

        String[] validFormats = {
                "yyyy-MM-dd",
                "MM/dd/yyyy",
                "dd-MM-yyyy",
                "yyyy/MM/dd",
                "MMMM dd, yyyy",
                "dd MMM yyyy",
                "yyyy-MMMM-dd"
        };

        boolean isValid = Arrays.stream(validFormats)
                .anyMatch(format -> isValidDateFormat(dateStr, format));

        if (isValid) {
            System.out.println("Date format is valid.");
        } else {
            System.out.println("Date format is not valid.");
        }
    }

    public static boolean isValidDateFormat(String dateStr, String format) {
        try {
            DateTimeFormatter.ofPattern(format).parse(dateStr);
            return true;
        } catch (DateTimeParseException e) {
            return false;
        }
    }
}