java.util.Date format conversion yyyy-mm-dd to mm-dd-yyyy

Question

I have a `java.util.Date` in the format `yyyy-mm-dd`. I want it to be in the format `mm-dd-yyyy` Below is the sample util I tried out for this conversion: ``` // Setting the pattern SimpleDateFormat sm = new SimpleDateFormat("mm-dd-yyyy"); // myDate is the java.util.Date in yyyy-mm-dd format // Converting it into String using formatter String strDate = sm.format(myDate); //Converting the String back to java.util.Date Date dt = sm.parse(strDate); ``` Still the output I am getting is not in the format `mm-dd-yyyy`. Kindly let me know how to format a `java.util.Date` from `yyyy-mm-dd` to `mm-dd-yyyy`

Accepted Answer

`Date` is a container for the number of milliseconds since the Unix epoch ( 00:00:00 UTC on 1 January 1970).

It has no concept of format.

Java 8+

```
LocalDateTime ldt = LocalDateTime.now();
System.out.println(DateTimeFormatter.ofPattern("MM-dd-yyyy", Locale.ENGLISH).format(ldt));
System.out.println(DateTimeFormatter.ofPattern("yyyy-MM-dd", Locale.ENGLISH).format(ldt));
System.out.println(ldt);
```

Outputs...

```
05-11-2018
2018-05-11
2018-05-11T17:24:42.980
```

Java 7-

You should be making use of the ThreeTen Backport

Original Answer

For example...

```
Date myDate = new Date();
System.out.println(myDate);
System.out.println(new SimpleDateFormat("MM-dd-yyyy").format(myDate));
System.out.println(new SimpleDateFormat("yyyy-MM-dd").format(myDate));
System.out.println(myDate);
```

Outputs...

```
Wed Aug 28 16:20:39 EST 2013
08-28-2013
2013-08-28
Wed Aug 28 16:20:39 EST 2013
```

None of the formatting has changed the underlying `Date` value. This is the purpose of the `DateFormatter`s

Updated with additional example

Just in case the first example didn't make sense...

This example uses two formatters to format the same date. I then use these same formatters to parse the `String` values back to `Date`s. The resulting parse does not alter the way `Date` reports it's value.

`Date#toString` is just a dump of it's contents. You can't change this, but you can format the `Date` object any way you like

```
try {
    Date myDate = new Date();
    System.out.println(myDate);

SimpleDateFormat mdyFormat = new SimpleDateFormat("MM-dd-yyyy");
    SimpleDateFormat dmyFormat = new SimpleDateFormat("yyyy-MM-dd");

// Format the date to Strings
    String mdy = mdyFormat.format(myDate);
    String dmy = dmyFormat.format(myDate);

// Results...
    System.out.println(mdy);
    System.out.println(dmy);
    // Parse the Strings back to dates
    // Note, the formats don't "stick" with the Date value
    System.out.println(mdyFormat.parse(mdy));
    System.out.println(dmyFormat.parse(dmy));
} catch (ParseException exp) {
    exp.printStackTrace();
}
```

Which outputs...

```
Wed Aug 28 16:24:54 EST 2013
08-28-2013
2013-08-28
Wed Aug 28 00:00:00 EST 2013
Wed Aug 28 00:00:00 EST 2013
```

Also, be careful of the format patterns. Take a closer look at `SimpleDateFormat` to make sure you're not using the wrong patterns ;)

java.util.Date format conversion yyyy-mm-dd to mm-dd-yyyy

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