在python中对日期进行操作的库有：datetime、time
无论在哪种语言，日期函数肯定是最常用的函数。下面直接上实例代码
#datetime
import datetime
#当前日期
now = datetime.datetime.now()
print(now.strftime('%Y-%m-%d %H:%M:%S'))
print(now.strftime('%Y-%m-%d'))
#string convert to datetime
time_str = '2013-07-29 09:05:00'
str_convert_2_time = datetime.datetime.strptime(time_str, '%Y-%m-%d %H:%M:%S')
print(str_convert_2_time)
#比较两个日期相差多少天
time_strA = '2013-07-29 09:05:00'
time_strB ='2013-08-29 09:05:00'
day = datetime.datetime.strptime(time_strA, '%Y-%m-%d %H:%M:%S')
day2 = datetime.datetime.strptime(time_strB, '%Y-%m-%d %H:%M:%S')
sub_day = day2 - day
print('{0}和{1}相差{2}天'.format(time_strA, time_strB, str(sub_day.days)))
#今后的n天的日期
n_days = 4
now = datetime.datetime.now()
my_date = datetime.timedelta(days=n_days)
n_day = now + my_date
print('从今天起的{0}天的日期是：'.format(n_days))
print(n_day.strftime('%Y-%m-%d %H:%M:%S'))运行结果：
>>>
2013-07-29 09:48:16
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2013-07-29
2013-07-29 09:05:00
2013-07-29 09:05:00和2013-08-29 09:05:00相差31天
从今天起的4天的日期是：
2013-08-02 09:48:16
>>>
