QString QDateTime::toString ( const QString & format ) const

QDateTime类的QString toString ( const QString & format ) const 函数用于格式化时间输入非常好。
例如：QDateTime::currentDateTime().toString("yyyy年MM月dd日 hh:mm:ss"); //输出为“2011年10月15日 18:22:13”
具体的格式设置Qt的文档中写得比较全：

These expressions may be used for the date:

Expression	Output
d	the day as number without a leading zero (1 to 31)
dd	the day as number with a leading zero (01 to 31)
ddd	the abbreviated localized day name (e.g. 'Mon' to 'Sun'). Uses QDate::shortDayName().
dddd	the long localized day name (e.g. 'Monday' to 'Qt::Sunday'). Uses QDate::longDayName().
M	the month as number without a leading zero (1-12)
MM	the month as number with a leading zero (01-12)
MMM	the abbreviated localized month name (e.g. 'Jan' to 'Dec'). Uses QDate::shortMonthName().
MMMM	the long localized month name (e.g. 'January' to 'December'). Uses QDate::longMonthName().
yy	the year as two digit number (00-99)
yyyy	the year as four digit number

These expressions may be used for the time:

Expression	Output
h	the hour without a leading zero (0 to 23 or 1 to 12 if AM/PM display)
hh	the hour with a leading zero (00 to 23 or 01 to 12 if AM/PM display)
m	the minute without a leading zero (0 to 59)
mm	the minute with a leading zero (00 to 59)
s	the second without a leading zero (0 to 59)
ss	the second with a leading zero (00 to 59)
z	the milliseconds without leading zeroes (0 to 999)
zzz	the milliseconds with leading zeroes (000 to 999)
AP	use AM/PM display. AP will be replaced by either "AM" or "PM".
ap	use am/pm display. ap will be replaced by either "am" or "pm".

All other input characters will be ignored. Any sequence of characters that are enclosed in singlequotes will be treated as text and not be used as an expression. Two consecutive singlequotes ("''") are replaced by a singlequote in the output.

Example format strings (assumed that the QDateTime is 21 May 2001 14:13:09):

Format	Result
dd.MM.yyyy	21.05.2001
ddd MMMM d yy	Tue May 21 01
hh:mm:ss.zzz	14:13:09.042
h:m:s ap	2:13:9 pm

If the datetime is invalid, an empty string will be returned.