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.
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
You should be making use of the ThreeTen Backport
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 ;)