How to Convert Java Date to XML DateTime String?

In order to define a date and time, the DateTime data type is used. DateTime is defined in the format as “YYYY-MM-DDThh:mm:ss” where:

• YYYY states the year
• MM represents the month
• DD shows the day
• T indicates the beginning of the time segment needed.
• Hh determines the hour
• mm represents the minute
• ss indicates the second

Example: 2002-05-30T09:00:00

What are Time Zones in XML DateTime format?

In order to specify a time zone, we can either enter a DateTime in UTC time by inserting a “Z” behind the time,

Example: 

2002-05-30T09:30:10Z  

Or we can determine an offset from the UTC time by adding a positive or negative time behind the time,

Example:  

2002-05-30T09:30:10-06:00
2002-05-30T09:30:10+06:00

So, The timezone may be defined as “Z” (UTC) or “(+|-)hh:mm.” Undefined timezones are called “undetermined.” The literal “Z”(Zulu) is used as a time-zone indicator, which indicates that the time is UTC when added at the end of a time.

What is Time Offset?

A time offset is an amount of time to be added or subtracted from the Coordinated Universal Time (UTC) time to get the current time of a specific place.

Approach to convert Java Date to XML DateTime String:

• Firstly we create an object of SimpleDateFormat. This class parses and formats the date and time in Java.
• Then, we create a StringBuffer which will hold the XML formatted string.
• Further, we calculate the ZoneOffset. It determines a time zone offset from Greenwich/UTC time. A time-zone offset is the amount of time that a time-zone differs from Greenwich/UTC. This is usually a fixed number of hours and minutes. Different parts of the world have different time-zone offsets. For example, India is 05:30 ahead of the Greenwich/UTC.
• At last, we combine all the required information in a single string, which is the formatted XML string.

Java

// Java program to Convert Java Date to XML DateTime String

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

public class GFG {

    public static void main(String[] args)
    {

        // formatting time
        SimpleDateFormat format1 = new SimpleDateFormat("yyyy-MM-dd");
        SimpleDateFormat format2 = new SimpleDateFormat("HH:mm:ss");

        // create a StringBuffer(in order to use its append
        // functionality) to store the date in XML DateTime
        // format
        StringBuffer buff = new StringBuffer();

        // get the date of the system by creating an
        // instance of the Date class
        Date date = new Date();

        // append the formatted date(yyyy-MM-dd) in the
        // buffer
        buff.append(format1.format(date));

        // append T
        buff.append('T');

        // and finally append the formatted time(HH:mm:ss) in
        // buffer
        buff.append(format2.format(date));

        // calculating time zone
        // get the calendar instance in order to get the
        // time offset
        Calendar calendar = Calendar.getInstance();

        // The get(int field_value) method of Calendar class
        // is used to return the value of the given calendar
        // field in the parameter.
        int offset = calendar.get(calendar.ZONE_OFFSET)
                     / (1000 * 60);

        // add the sign(+/-) according to the value of the
        // offset
        if (offset < 0) {
            buff.append('-');

            // if the offset is negative make it positive by
            // multiplying it with -1, we will be using it
            //further
            offset *= -1;
        }
        else {
            buff.append('+');
        }

        // get the hour from the offset and store it in a
        // String
        String s1 = String.valueOf(offset / 60);

        // check if the retrieved hour is single digit or
        // two digit in case of single digit, add 0 before
        // the significant value
        for (int i = s1.length(); i < 2; i++) {
            buff.append('0');
        }

        // then finally append the s1 in our buffer
        buff.append(s1);
        buff.append(':');

        // now retrieve the minutes from offset, and
        // validate it in the same way as we did for the hour
        String s2 = String.valueOf(offset % 60);

        for (int i = s2.length(); i < 2; i++) {
            buff.append('0');
        }

        // append the minutes in buffer
        buff.append(s2);

        // finally we are done formatting the Java Date time
        // into XML DateTime format convert the buffer into
        // the String, and print it
        System.out.println(buff.toString());
    }
}

Output

2021-02-23T10:38:30+00:00