Simple Date Format error parsing date

Question

I have an issue with a Simple Date Format, I don't know why. This is my algorithm

if (realtimeDeparture != null) {
        int hours = this.realtimeDeparture / 3600;
        int minutes = (this.realtimeDeparture % 3600) / 60;
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd hh:mm");
        try {
            Calendar cal = Calendar.getInstance(Locale.FRENCH);
            String date = cal.get(Calendar.YEAR) + "-" + (cal.get(Calendar.MONTH)+1)+ "-" + cal.get(Calendar.DAY_OF_MONTH)+ " " + hours+":"+minutes;
            result = df.parse(date);
}

I have an API which give me a number of seconds after 00h00 (realtimeDeparture) I want to extract from this integer a real Date Object So I did this algorithm but I loose hour I don't know why.

For example, there is some input and result value :

date = 2018-5-7 12:26
result = Mon May 07 00:26:00 GMT+02:00 2018

I tried to check if 07/05/2018 is different than 7/5/2018, but same issue :

date = 2018-05-07 12:26 
result = Mon May 07 00:26:00 GMT+02:00 2018

How I can get my Date Object from a number of second from 00h00 ? Or how I can fix my algorithm ?

Answer 1

Your calculation looks fine to me so my guess is the issue is the formatting.

Have you tried using

cal.set(Calendar.HOUR_OF_DAY, hours);
cal.set(Calendar.MINUTE, minutes);

and then getting the date with

Date date = cal.getTime();

Answer 2

Using java.time, the modern Java date and time API, this is so much easier, more straightforward and less error-prone:

    int realtimeDeparture = 44783;
    LocalTime time = LocalTime.ofSecondOfDay(realtimeDeparture);
    System.out.println(time);

This prints:

12:26:23

If you need today’s date at the time of day in question, you need to decide a time zone first, for example:

    ZoneId zone = ZoneId.of("Asia/Bangkok");
    ZonedDateTime dateTime = LocalDate.now(zone).atTime(time).atZone(zone);
    System.out.println(dateTime);

2018-05-07T12:26:23+07:00[Asia/Bangkok]

Question: Why do I need a time zone? Because it is never the same date everywhere on earth. You may specify ZoneId.systemDefault() in order to use the JVM’s time zone setting, which in turn usually comes from the device. It may, however, be changed at any time from another part of your program or another program running in the same JVM.

What went wrong in your code?

In your format pattern string you are using lowercase hh for hours, 12 in your example. hh is for hour within AM or PM, from 01 through 12. When you don’t specify AM or PM, SimpleDateFormat uses AM as default. 12:26 AM means 26 minutes past midnight, the same as 00:26 on a 24 hour clock. So this was what SimpleDateFormat gave you.

You were sort of lucky to test with hour-of-day of 12. Other hours of day work as you would have expected in spite of your bug. Others have made the same error, and it has gone unnoticed for long. For comparison, the modern API would in a similar situation have thrown an exception to make you aware of the missing AM/PM marker. I clearly prefer this behaviour.

Question: Can I use java.time on Android?

Yes, java.time works nicely on older and newer Android devices. It just requires at least Java 6.

• In Java 8 and later and on newer Android devices (from API level 26, I’m told) the modern API comes built-in.
• In Java 6 and 7 get the ThreeTen Backport, the backport of the new classes (ThreeTen for JSR 310; see the links at the bottom).
• On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.

Links

• Oracle tutorial: Date Time explaining how to use java.time.
• Java Specification Request (JSR) 310, where java.time was first described.
• ThreeTen Backport project, the backport of java.timeto Java 6 and 7 (ThreeTen for JSR-310).
• ThreeTenABP, Android edition of ThreeTen Backport
• Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.

Answer 3

Try this code..

   String date=" 2018-5-7 12:26";
    SimpleDateFormat spf=new SimpleDateFormat("yyyy-mm-dd hh:mm");
    Date newDate= null;
    try {
        newDate = spf.parse(date);
    } catch (ParseException e) {
        e.printStackTrace();
    }
    spf= new SimpleDateFormat("EEE MMM dd hh:mm:ss zzz yyyy", Locale.ENGLISH);
    date = spf.format(newDate);
    System.out.println(date);

then object want to convert like below code..

        try {
        Date dateToshow=spf.parse(date);
        Log.d("Date object:",dateToshow.toString());
    } catch (ParseException e) {
        e.printStackTrace();
    }