Python Date and Time
# The "time" module is the most basic.
# Date/time values are stored as seconds since 1970-01-01 or as 9-element tuples
# Item Meaning Field name Range Notes
# 0 Year tm_year 1970-2038 Wider on some platforms
# 1 Month tm_mon 1-12 1 is January; 12 is December
# 2 Day tm_mday 1-31
# 3 Hour tm_hour 0-23 0 is midnight; 12 is noon
# 4 Minute tm_min 0-59
# 5 Second tm_sec 0-61 60 and 61 for leap seconds
# 6 Weekday tm_wday 0-6 0 is Monday; 6 is Sunday
# 7 Year day tm_yday 1-366 Day number within the year
# 8 DST flag tm_isdst -1 to 1 -1 means library determines DST
import time
# convert string to time tuple
x = time.strptime('2006-04-13', '%Y-%m-%d') # (2006, 4, 13, 0, 0, 0, 3, 103, -1)
x.tm_year # 2006
x.tm_wday # 3 (Thursday)
# convert time tuple to string
time.strftime('%Y-%m-%d', x) # '2006-04-13'
# convert time tuple to seconds
seconds = time.mktime(x) # 1144911600.0
# convert seconds to time tuple
time.localtime(seconds) # (2006, 4, 13, 0, 0, 0, 3, 103, 1)
# get current time as tuple
time.localtime() # (2006, 6, 16, 10, 2, 3, 4, 167, 1)
Full date format syntax: http://unixhelp.ed.ac.uk/CGI/man-cgi?date
Date arithmetic
import datetime
day = datetime.date(2008, 6, 23)
day.isoformat() # '2008-06-23'
datetime.date.today().isoformat() # '2011-01-05'
week = datetime.timedelta(days=7)
(day+week).isoformat() # '2008-06-30'
yesterday = datetime.date.today() - datetime.timedelta(days=1)
Measuring elapsed time
time.clock() # returns a float representing some number of seconds
On Unix, return the current processor time as a floating point number expressed in seconds. The precision, and in fact the very definition of the meaning of "processor time", depends on that of the C function of the same name, but in any case, this is the function to use for benchmarking Python or timing algorithms.
On Windows, this function returns wall-clock seconds elapsed since the first call to this function, as a floating point number, based on the Win32 function QueryPerformanceCounter(). The resolution is typically better than one microsecond.
datetime Module
import datetime
t1 = datetime.datetime.strptime("2011-05-10T05:19:47Z", "%Y-%m-%dT%H:%M:%SZ")
t2 = datetime.datetime.strptime("2011-05-10T05:20:06Z", "%Y-%m-%dT%H:%M:%SZ")
elapsed = t2 - t1
print elapsed.seconds