How to convert UTC date and time format to zone time format?

Question

I have a method which generates a random date and time.

import java.text.SimpleDateFormat;
import java.time.LocalDateTime;
import java.time.Period;

public String getRandomFormattedDateAndTime() {
    LocalDateTime date = generateRandomDateAndTimeInPast();
    return formatDate(date);
}
        
public LocalDateTime generateRandomDateAndTimeInPast() {
    return LocalDateTime.now()
                        .minus(Period.ofDays(
                            (new Random().nextInt(365 * 2))
                        ));
}

  public static String formatDate(LocalDateTime date) {
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(DATE_TIME_FORMAT_PATTERN);
    return dateTimeFormatter.format(date);
  }

and the printed output is something like "2020-08-07T08:57:09Z"

However, i need to obtain the same value with time zone format 2020-08-07T10:57:09+02:00 which has the +02:00 (my local time).

I have seen several questions and pages like this, but they do not give me a clue.

Answer 1

I hope this is what you are looking for:

ZonedDateTime  zonedDateTime = ZonedDateTime.now().minus(Period.ofDays((new Random().nextInt(365 * 2))));
System.out.println("Date Time:" + zonedDateTime.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME));
        

Output: Date Time:2019-07-13T14:27:51.909+05:30

Note: 05:30 is my time zone (local) offset

Answer 2

In your example you're using the type LocalDateTime. LocalDateTime can't be formatted with timezone pattern as it doesn't contains any timezone information...

Switch to ZonedDateTime will solve your problem.

Answer 3

Not sure why people are involving ZonedDateTime here, but it seems to be a valid approach...

However, I want to add another one, that is the use of an OffsetDateTime.

This is an adjusted version of your method generateRandomDateAndTimeInPast:

public static OffsetDateTime generateRandomDateAndTimeInPast(int offset) {
    return OffsetDateTime.now(ZoneOffset.ofHours(offset))
                        .minusDays(
                            ThreadLocalRandom.current()
                                            .nextInt(365 * 2)
                        );
}

An example use could look like this, please note the implicit call to OffsetDateTime.toString() by directly System.outing the instance of OffsetDateTime. You can alter the output by calling OffsetDateTime.format(DateTimeFormatter).

public static void main(String[] args) {
    OffsetDateTime odt = generateRandomDateAndTimeInPast(2);
    System.out.println(odt);
}

This prints out datetimes formatted like the following (randomly generated) one:

2020-10-14T10:44:23.304+02:00

If you need a LocalDateTime (that won't contain or print any offset), you can simply get it from the OffsetDateTime like this:

LocalDateTime ldt = odt.toLocalDateTime();

A ZonedDateTime has that method, too, so if you use that or an OffsetDateTime you can always have the LocalDateTime they are based on by calling toLocalDateTime().

Answer 4

You have not provided the code of your method, formatDate(LocalDate). However, you have mentioned that String getRandomFormattedDateAndTime() is returning you 2020-08-07T08:57:09Z. The following method, getDateTimeInMyTz(String) provides you with what you are looking for:

import java.time.Instant;
import java.time.ZoneId;
import java.time.ZoneOffset;

public class Main {
    public static void main(String[] args) {
        // Test
        System.out.println(getDateTimeInMyTz("2020-08-07T08:57:09Z"));
    }

    public static String getDateTimeInMyTz(String strDtUtc) {
        Instant instant = Instant.parse(strDtUtc);
        ZoneOffset offset = ZoneId.systemDefault().getRules().getOffset(instant);
        return instant.atOffset(offset).toString();
    }
}

Output in my timezone which has an offset of +01:00 hours:

2020-08-07T09:57:09+01:00

Usage: Replace getDateTimeInMyTz("2020-08-07T08:57:09Z") with getDateTimeInMyTz(getRandomFormattedDateAndTime()).

If you share the code of your method, formatDate(LocalDate), I can suggest further simplification.

Learn more about java.time, the modern Date-Time API^* from Trail: Date Time.

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^{* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.}