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javadatecalendar

Java formatting GMT Date

I'm not finding a way to do edit GMT Date

I receive "params.date" one string in this format "yyyyMMdd", so this is my flow:

Date date = new SimpleDateFormat('yyyyMMdd').parse(params.data)
System.out.println(sdf.parse(params.data))

output:

Thu Nov 17 21:00:00 GMT-03:00 2022

And I need it:

Thu Nov 17 21:00:00 GMT-00:00 2022

Can someone help me?

Solution

  • A few important points:

    1. Thu Nov 17 21:00:00 GMT-03:00 2022 is not equal to Thu Nov 17 21:00:00 GMT-00:00 2022. The date-time of Thu Nov 17 21:00:00 GMT-03:00 2022 is equal to the date-time of Fri Nov 18 00:00:00 GMT+00:00 2022 which you can obtain by adding 3 hours to Thu Nov 17 21:00:00 GMT-03:00 2022.
    2. Your time-zone has an offset of -03:00 and therefore the java.util.Date object is being displayed with the default time-zone offset. Note that java.util.Date does not represent a real date-time, rather, it gives you the number of milliseconds from the Epoch and then the Date#toString implementation applies the system's time-zone to render the string.
    3. The java.util date-time API and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern date-time API.

    Demo with java.time API:

    import java.time.LocalDate;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {

        public static void main(String[] args) {
                String data = "20221118";
                LocalDate date = LocalDate.parse(data, DateTimeFormatter.BASIC_ISO_DATE);

                ZonedDateTime zdt1 = date.atStartOfDay(ZoneOffset.UTC);
                ZonedDateTime zdt2 = zdt1.withZoneSameInstant(ZoneOffset.of("-03:00"));

                DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss 'GMT'xxx uuuu",
                                Locale.ENGLISH);
                System.out.println(formatter.format(zdt2));
                System.out.println(formatter.format(zdt1));
        }
}

    Output:

    Thu Nov 17 21:00:00 GMT-03:00 2022
Fri Nov 18 00:00:00 GMT+00:00 2022

    Learn more about the modern Date-Time API from Trail: Date Time.