Time not adding

Question

I'm trying to get it to be 12 hours ahead of what it is, it doesn't work but anything lower works, unsure on how to fix it.

package New;
import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
public class DateManipulation {

public static void main(String[] args) {
    Date date = new Date();
    String test = new SimpleDateFormat("MM-dd-yy").format(date);
    System.out.println(test);
    DateFormat sdf = new SimpleDateFormat("hh:mm:ss");
    try {
        date.setTime(date.getTime()+43200000l);
        String time = sdf.format(date);
        System.out.println(time);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

}

HMU With any solutions

Btw I've tried making a long variable with the value of 43200000l then tried adding but still didn't working, been stuck on this for 30 minutes and haven't found anything. — INeedHelp, Feb 22 '16 at 23:24
FYI, the troublesome old date-time classes such as [`java.util.Date`](https://docs.oracle.com/javase/9/docs/api/java/util/Date.html), [`java.util.Calendar`](https://docs.oracle.com/javase/9/docs/api/java/util/Calendar.html), and `java.text.SimpleDateFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [*java.time*](https://docs.oracle.com/javase/9/docs/api/java/time/package-summary.html) classes built into Java 8 & Java 9. See [*Tutorial* by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). — Basil Bourque, Mar 25 '18 at 18:52

score 4 · Accepted Answer · answered Feb 22 '16 at 23:27

The first thing to note is h in SimpleDateFormat represents the "Hour in am/pm (1-12)"

So, 10am + 12 is 10pm, but since you've not supplied a formatter for the am/pm marker, it's basically just 10...

Now days, the preferred method would be to use Java 8's Time API or Joda-Time, for example...

LocalDateTime dateTime = LocalDateTime.now();
System.out.println(DateTimeFormatter.ofPattern("MM-dd-yy HH:mm:ss").format(dateTime));
LocalDateTime later = dateTime.plusHours(12);
System.out.println(DateTimeFormatter.ofPattern("MM-dd-yy HH:mm:ss").format(later));

Which outputs...

02-23-16 10:27:27
02-23-16 22:27:27

I've deliberately used HH to show that it works

Sorry, I clicked the wrong place. Deleted. – Basil Bourque Mar 25 '18 at 19:22 — Basil Bourque, Mar 25 '18 at 19:22

score 0 · Answer 2 · edited Feb 23 '16 at 00:32

0

Try the new Date&Time API (java.time) of Java 8 and later. It is much more simple. See Tutorial.

LocalTime time = LocalTime.now(); 
LocalTime newTime = time.plusHours(12);

edited Feb 23 '16 at 00:32

Basil Bourque

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answered Feb 22 '16 at 23:28

E_d

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But it they use a format of `hh:mm:ss` in `DateTimeFormatter`, they'll still have the same problem – MadProgrammer Feb 22 '16 at 23:28
As you said "_since you've not supplied a formatter for the am/pm marker, it's basically just 10_" – E_d Feb 22 '16 at 23:36
1

So, the point been, the answer isn't "use Java 8's Time API" (although highly recommended), the answer is, use a better format ;) – MadProgrammer Feb 22 '16 at 23:59
1

Also, I suggest always specifying the desired/expected time zone when calling `.now` rather than implicitly relying on the JVM’s current default time zone. `LocalTime.now( ZoneId.of( "America/Montreal" ) )` – Basil Bourque Feb 23 '16 at 00:35

Time not adding

2 Answers2