Calendar formatting issues

Question

We're searching for information on how to format instances of java.util.Calendar and more general information and coding hints regarding transition from using java.util.Date to java.util.Calendar.

best, phil

Has the [official documentation](http://java.sun.com/j2se/1.5.0/docs/api/java/util/Calendar.html) not proven useful? — Justin L., Jun 16 '10 at 07:38
If you really cannot avoid getting an old-fashioned `Calendar`, convert to a modern `ZonedDateTime` using `((GregorianCalendar) yourCalendar).toZonedDateTime()` and format the resulting object as shown in the answer by Arvind Kumar Avinash. — Ole V.V., Jul 15 '21 at 06:22

score 3 · Answer 1 · answered Jun 16 '10 at 07:37

My hint would be not to use either Date or Calendar. Use Joda Time instead. It's much, much nicer than the built-in classes. JSR-310 will hopefully, eventually bring something Joda-like into the main library, but for the moment Joda is your best bet.

If you must stick to Date/Calendar, see java.text.DateFormat and java.text.SimpleDateFormat. Remember that they're not thread-safe though :(

score 2 · Answer 2 · answered Jul 14 '21 at 19:32

java.time

The java.util Date-Time API and their formatting API, SimpleDateFormat are outdated and error-prone.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^*.

Also, quoted below is a notice from the home page of Joda-Time:

Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.

Solution using java.time, the modern Date-Time API:

If you are getting an object of java.util.Date from some API, your first step should be to convert it into Instant using Date#toInstant which can be converted to other types of modern Date-Time API.

A demo with the modern Date-Time API:

import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.OffsetDateTime;
import java.time.ZoneId;
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) {
        Instant instant = Instant.now();
        System.out.println(instant);

        ZonedDateTime zdtUtc = instant.atZone(ZoneId.of("Etc/UTC"));
        System.out.println(zdtUtc);
        ZonedDateTime zdtNewYork = instant.atZone(ZoneId.of("America/New_York"));
        System.out.println(zdtNewYork);

        // Fixed offset
        OffsetDateTime odtUtc = instant.atOffset(ZoneOffset.UTC);
        System.out.println(odtUtc);
        OffsetDateTime odtWithOffset0530Hours = instant.atOffset(ZoneOffset.of("+05:30"));
        System.out.println(odtWithOffset0530Hours);

        // OffsetDateTime from ZonedDateTime
        OffsetDateTime odtNewYork = zdtNewYork.toOffsetDateTime();
        System.out.println(odtNewYork);

        // LocalDate in New York
        LocalDate todayNewYork = zdtNewYork.toLocalDate();
        System.out.println(todayNewYork);
        // Alternatively
        System.out.println(LocalDate.now(ZoneId.of("America/New_York")));

        // LocalDateTime in New York
        LocalDateTime nowNewYork = zdtNewYork.toLocalDateTime();
        System.out.println(nowNewYork);
        // Alternatively
        System.out.println(LocalDateTime.now(ZoneId.of("America/New_York")));

        // Formatted output
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEE MMMM dd HH:mm:ss z uuuu", Locale.ENGLISH);
        System.out.println(dtf.format(zdtNewYork));
    }
}

Output:

2021-07-14T19:22:13.544911Z
2021-07-14T19:22:13.544911Z[Etc/UTC]
2021-07-14T15:22:13.544911-04:00[America/New_York]
2021-07-14T19:22:13.544911Z
2021-07-15T00:52:13.544911+05:30
2021-07-14T15:22:13.544911-04:00
2021-07-14
2021-07-14
2021-07-14T15:22:13.544911
2021-07-14T15:22:13.586971
Wed July 14 15:22:13 EDT 2021

ONLINE DEMO

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

Some helpful answers using java.time API:

Check this answer and this answer to learn how to use java.time API with JDBC.
How to use ParsePostion?
Timezone conversion.
SimpleDateFormat does not handle fraction-of-second beyond three digits in the millisecond part correctly.
How to convert LocalDate to ZonedDateTime?
'Z' is not the same as Z.
Day-of-month with ordinal.
The standard library does not support a formatted Date-Time object.
Never use SimpleDateFormat or DateTimeFormatter without a Locale.
How to check if timestamp (epoch time) is of today's or yesterday's?

^{* 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.}

Calendar formatting issues

2 Answers2

java.time