时间格式化语法：
为了指定时间格式要使用到一个时间格式串。用法如下

Symbol Meaning Presentation Example
　　-- 　　--- 　　　　　　 　　---
G era designator (Text) AD
y year (Number) 1996
M month in year (Text & Number) July & 07
d day in month (Number) 10
h hour in am/pm (1~12) (Number) 12
H hour in day (0~23) (Number) 0
m minute in hour (Number) 30
s second in minute (Number) 55
S millisecond (Number) 978
E day in week (Text) Tuesday
D day in year (Number) 189
F day of week in month (Number) 2 (2nd Wed in July)
w week in year (Number) 27
W week in month (Number) 2
a am/pm marker (Text) PM
k hour in day (1~24) (Number) 24
K hour in am/pm (0~11) (Number) 0
z time zone (Text) Pacific Standard Time
' escape for text (Delimiter)
'' single quote (Literal) '

下面是使用美国当地时间格式的例子：

Format Pattern Result
　　　　　　-- 　　---
"yyyy.MM.dd G 'at' hh:mm:ss z" ->> 1996.07.10 AD at 15:08:56 PDT
"EEE, MMM d, ''yy" ->> Wed, July 10, '96
"h:mm a" ->> 12:08 PM
"hh 'o''clock' a, zzzz" ->> 12 o'clock PM, Pacific Daylight Time
"K:mm a, z" ->> 0:00 PM, PST
"yyyyy.MMMMM.dd GGG hh:mm aaa" ->> 1996.July.10 AD 12:08 PM


代码示例：
<%@page import="java.text.SimpleDateFormat"%>
<%
// Format the current time.
SimpleDateFormat formatter
= new SimpleDateFormat ("yyyy-MM-dd '' HH:mm:ss");//将显示"1999-10-1 21:03:10"的格式.
Date currentTime_1 = new Date();
String dateString = formatter.format(currentTime_1);

out.println("时间格式：");
out.println(dateString);
%>