From：http://www.cnblogs.com/65702708/archive/2011/04/17/2018936.html
http://www.wklken.me/posts/2015/03/03/python-base-datetime.html
Python格式化日期时间的函数为datetime.datetime.strftime()；由字符串转为日期型的函数为：datetime.datetime.strptime()，两个函数都涉及日期时间的格式化字符串，列举如下：
1 %a Abbreviated weekday name
2 %A Full weekday name
3 %b Abbreviated month name
4 %B Full month name
5 %c Date and time representation appropriate for locale
6 %d Day of month as decimal number (01 - 31)
7 %H Hour in 24-hour format (00 - 23)
8 %I Hour in 12-hour format (01 - 12)
9 %j Day of year as decimal number (001 - 366)
10 %m Month as decimal number (01 - 12)
11 %M Minute as decimal number (00 - 59)
12 %p Current locale's A.M./P.M. indicator for 12-hour clock
13 %S Second as decimal number (00 - 59)
14 %U Week of year as decimal number, with Sunday as first day of week (00 - 51)
15 %w Weekday as decimal number (0 - 6; Sunday is 0)
16 %W Week of year as decimal number, with Monday as first day of week (00 - 51)
17 %x Date representation for current locale
18 %X Time representation for current locale
19 %y Year without century, as decimal number (00 - 99)
20 %Y Year with century, as decimal number
21 %z, %Z Time-zone name or abbreviation; no characters if time zone is unknown
22 %% Percent sign
举一个例子：
ebay中时间格式为‘Sep-21-09 16:34’
则通过下面代码将这个字符串转换成datetime
c = datetime.datetime.strptime('Sep-21-09 16:34','%b-%d-%y %H:%M');
#打印C
c
datetime.datetime(2009, 9, 21, 16, 34)
又如：datetime转换成字符串
datetime.datetime.now().strftime('%b-%d-%y %H:%M:%S'); 'Sep-22-09 16:48:08'