1.把字符串转换为datetime
from datetime import datetime
begin_date = datetime.strptime("2013-07-01",'%Y-%m-%d')
2.把当前时间转换为0点0分：
from datetime import datetime
now = datetime.now()
now.strftime("%Y-%m-%dT00:00:00Z")
输出： '2013-07-29T00:00:00Z'
3. 日期差，比如获取1小时以前的日期
import datetime m = datetime.datetime.now() print m + datetime.timedelta(hours=1) print m - datetime.timedelta(minutes=10)
Python关于时间日期有两个库datetime和time，于是我们要在四种格式之间转换：
datetime.datetime对象 datetime.datetime.now()
time.struct_time对象 time.localtime()
字符串 "2010-12-04T10:30:53"
时间戳 1291433453 （一般我们不关心微秒）
列一下它们的转换方法：
dt = datetime.datetime(2010, 12, 4, 10, 30, 53)
dt = datetime.datetime.strptime("2010-12-04T10:30:53", "%Y-%m-%dT%H:%M:%S")
dt.strftime("%Y-%m-%dT%H:%M:%S") -> "2010-12-04T10:30:53"
或者 dt.isoformat().split(".").pop(0) -> "2010-12-04T10:30:53"
dt = datetime.datetime.fromtimestamp(1291433453)
(?) dt -> 1291433453
t = time.localtime(1291433453)
t = dt.timetuple()
t = time.strptime("2010-12-04T10:30:53", "%Y-%m-%dT%H:%M:%S")
t.strftime("%Y-%m-%dT%H:%M:%S") -> "2010-12-04T10:30:53"
long( time.mktime(t) ) -> 1291433453
(?) t -> dt
可以看出，Python没有提供直接的time.struct_time对象到datetime.datetime对象的转换，也没有直接提供datetime.datetime对象到时间戳的转换。另外，Python的两个strftime ，strptime中都没有时间戳的格式化符号。
对time.struct_time对象到datetime.datetime对象的转换,很容易想到通过字符串形式过渡一下：
dt = datetime.datetime.strptime(t.strftime("%Y-%m-%dT%H:%M:%S"), "%Y-%m-%dT%H:%M:%S")
格式化：
import datetime
now = datetime.datetime.now()
now.strftime("%y%m")
now.strftime("%H-%M-%S")
format：
| %a | Locale’s abbreviated weekday name. | |
| %A | Locale’s full weekday name. | |
| %b | Locale’s abbreviated month name. | |
| %B | Locale’s full month name. | |
| %c | Locale’s appropriate date and time representation. | |
| %d | Day of the month as a decimal number [01,31]. | |
| %H | Hour (24-hour clock) as a decimal number [00,23]. | |
| %I | Hour (12-hour clock) as a decimal number [01,12]. | |
| %j | Day of the year as a decimal number [001,366]. | |
| %m | Month as a decimal number [01,12]. | |
| %M | Minute as a decimal number [00,59]. | |
| %p | Locale’s equivalent of either AM or PM. | (1) |
| %S | Second as a decimal number [00,61]. | (2) |
| %U | Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0. | (3) |
| %w | Weekday as a decimal number [0(Sunday),6]. | |
| %W | Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0. | (3) |
| %x | Locale’s appropriate date representation. | |
| %X | Locale’s appropriate time representation. | |
| %y | Year without century as a decimal number [00,99]. | |
| %Y | Year with century as a decimal number. | |
| %Z | Time zone name (no characters if no time zone exists). | |
| %% | A literal '%' character. |
python的日期和java日期转换
本来想通过long类型来处理，没想到python和java有点不同：
python
>>> time.time()
1349153802.826779
>>> datetime.fromtimestamp(1349153802)
datetime.datetime(2012, 10, 2, 12, 56, 42)
Date date = new Date(1349153802000l);
System.out.println(date.getTime());
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
System.out.print(df.format(date));