工作中遇到了很多需要时间转换的时候，记录一下，也不用每次都查看啦
1.日期格式化
我用time模块比较多，也可以使用datetime.datetime模块
1）str转date型
time.strptime(date_str, format)
2）date型转str
time.strftime(format, date_tuple)
3）timestamp转date
datetime.datetime.fromtimestamp(int(timestamp)).strftime(time_format)
4）date转timestamp
int(time.mktime(datetime.datetime.strptime(date, time_format).timetuple()))
2.日期加减
在datetime模块中有timedelta类，这个类的对象用于表示一个时间间隔，比如两个日期或者时间的差别，也可以用于直接计算日期时间的加减。
1）两个日期相差多少天
day1 = datetime.datetime.strptime('2016-03-29', '%Y-%m-%d') day2 = datetime.datetime.strptime('2016-03-25', '%Y-%m-%d') delta = day1 - day2 print delta.days
2）某一个时间的第N天
s_t = datetime.datetime.strptime(sometime_str, time_format)
s_t = s_t + datetime.timedelta(days=day_add)
3.关于format参数
%a Abbreviated weekday name
%A Full weekday name
%b Abbreviated month name
%B Full month name
%c Date and time representation appropriate for locale
%d Day of month as decimal number (01 - 31)
%H Hour in 24-hour format (00 - 23)
%I Hour in 12-hour format (01 - 12)
%j Day of year as decimal number (001 - 366)
%m Month as decimal number (01 - 12)
%M Minute as decimal number (00 - 59)
%p Current locale's A.M./P.M. indicator for 12-hour clock
%S Second as decimal number (00 - 59)
%U Week of year as decimal number, with Sunday as first day of week (00 - 51)
%w Weekday as decimal number (0 - 6; Sunday is 0)
%W Week of year as decimal number, with Monday as first day of week (00 - 51)
%x Date representation for current locale
%X Time representation for current locale
%y Year without century, as decimal number (00 - 99)
%Y Year with century, as decimal number
%z, %Z Time-zone name or abbreviation; no characters if time zone is unknown
%% Percent sign