You want to print the date and/or time in a specified format.

Use a java.text.DateFormat.

To print the date in the correct format for whatever locale your software lands in, simply use the default DateFormat formatter, which is obtained by calling DateFormat.getInstance( ) .

Suppose you want the date printed, but instead of the default format “Sun Jul 18 16:14:09 PDT 1999”, you want it printed like “Sun 1999.07.18 at 04:14:09 PM PDT”. A look at the Javadoc page for SimpleDateFormat -- the only non-abstract subclass of DateFormat -- reveals that it has a rich language for specifying date and time formatting. To use a default format, of course, we can just use the Date object’s toString( ) method, and for a localized default format, we use DateFormat.getInstance( ). But to have full control and get the “Sun 1999.07.18 at 04:14:09 PM PDT”, we construct an instance explicitly, like so:

new SimpleDateFormat ("E yyyy.MM.dd 'at' hh:mm:ss a zzz");

E means the day of the week; yyyy, MM, and dd are obviously year, month, and day. The quoted string 'at' means the string “at”. hh:mm:ss is the time; a means A.M. or P.M., and zzz means the time zone. Some of these are more memorable than others; I find the zzz tends to put me to sleep. Here’s the code:

// DateDemo.java 
Date dNow = new Date(  ); 
 
/* Simple, Java 1.0 date printing */ 
System.out.println("It is now " + dNow.toString(  )); 
 
// Use a SimpleDateFormat to print the date our way. 
SimpleDateFormat formatter 
    = new SimpleDateFormat ("E yyyy.MM.dd 'at' hh:mm:ss a zzz"); 
System.out.println("It is " + formatter.format(dNow));

There are many format symbols; a list is shown in Table 6-1.

You can use as many of the given symbols as needed. Where a format can be used either in text or numeric context, you can set it to longer form by repetitions of the character. For codes marked “Text”, four or more pattern letters will cause the formatter to use the long form, whereas fewer will cause it to use the short or abbreviated form if one exists. Thus, E might yield Mon, whereas EEEE would yield Monday. For those marked “Number”, the number of repetitions of the symbol gives the minimum number of digits. Shorter numbers are zero-padded to the given number of digits. The year is handled specially: yy yields a two-digit year (98, 88, 00, 01 . . . ), whereas yyyy yields a valid year (2001). For those marked “Text and Number”, three or more symbols causes it to use text, while one or two make it use a number: MM might yield 01, while MMM would yield January.