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=============
relativedelta
=============
.. automodule:: dateutil.relativedelta
:members:
:undoc-members:
.. testsetup:: relativedelta
Examples
--------
>>> from datetime import *; from dateutil.relativedelta import *
>>> import calendar
>>> NOW = datetime(2003, 9, 17, 20, 54, 47, 282310)
>>> TODAY = date(2003, 9, 17)
Let's begin our trip::
>>> from datetime import *; from dateutil.relativedelta import *
>>> import calendar
Store some values::
>>> NOW = datetime.now()
>>> TODAY = date.today()
>>> NOW
datetime.datetime(2003, 9, 17, 20, 54, 47, 282310)
>>> TODAY
datetime.date(2003, 9, 17)
Next month
.. doctest:: relativedelta
>>> NOW+relativedelta(months=+1)
datetime.datetime(2003, 10, 17, 20, 54, 47, 282310)
Next month, plus one week.
.. doctest:: relativedelta
>>> NOW+relativedelta(months=+1, weeks=+1)
datetime.datetime(2003, 10, 24, 20, 54, 47, 282310)
Next month, plus one week, at 10am.
.. doctest:: relativedelta
>>> TODAY+relativedelta(months=+1, weeks=+1, hour=10)
datetime.datetime(2003, 10, 24, 10, 0)
Here is another example using an absolute relativedelta. Notice the use of
year and month (both singular) which causes the values to be *replaced* in the
original datetime rather than performing an arithmetic operation on them.
.. doctest:: relativedelta
>>> NOW+relativedelta(year=1, month=1)
datetime.datetime(1, 1, 17, 20, 54, 47, 282310)
Let's try the other way around. Notice that the
hour setting we get in the relativedelta is relative,
since it's a difference, and the weeks parameter
has gone.
.. doctest:: relativedelta
>>> relativedelta(datetime(2003, 10, 24, 10, 0), TODAY)
relativedelta(months=+1, days=+7, hours=+10)
One month before one year.
.. doctest:: relativedelta
>>> NOW+relativedelta(years=+1, months=-1)
datetime.datetime(2004, 8, 17, 20, 54, 47, 282310)
How does it handle months with different numbers of days?
Notice that adding one month will never cross the month
boundary.
.. doctest:: relativedelta
>>> date(2003,1,27)+relativedelta(months=+1)
datetime.date(2003, 2, 27)
>>> date(2003,1,31)+relativedelta(months=+1)
datetime.date(2003, 2, 28)
>>> date(2003,1,31)+relativedelta(months=+2)
datetime.date(2003, 3, 31)
The logic for years is the same, even on leap years.
.. doctest:: relativedelta
>>> date(2000,2,28)+relativedelta(years=+1)
datetime.date(2001, 2, 28)
>>> date(2000,2,29)+relativedelta(years=+1)
datetime.date(2001, 2, 28)
>>> date(1999,2,28)+relativedelta(years=+1)
datetime.date(2000, 2, 28)
>>> date(1999,3,1)+relativedelta(years=+1)
datetime.date(2000, 3, 1)
>>> date(2001,2,28)+relativedelta(years=-1)
datetime.date(2000, 2, 28)
>>> date(2001,3,1)+relativedelta(years=-1)
datetime.date(2000, 3, 1)
Next friday
.. doctest:: relativedelta
>>> TODAY+relativedelta(weekday=FR)
datetime.date(2003, 9, 19)
>>> TODAY+relativedelta(weekday=calendar.FRIDAY)
datetime.date(2003, 9, 19)
Last friday in this month.
.. doctest:: relativedelta
>>> TODAY+relativedelta(day=31, weekday=FR(-1))
datetime.date(2003, 9, 26)
Next wednesday (it's today!).
.. doctest:: relativedelta
>>> TODAY+relativedelta(weekday=WE(+1))
datetime.date(2003, 9, 17)
Next wednesday, but not today.
.. doctest:: relativedelta
>>> TODAY+relativedelta(days=+1, weekday=WE(+1))
datetime.date(2003, 9, 24)
Following
[http://www.cl.cam.ac.uk/~mgk25/iso-time.html ISO year week number notation]
find the first day of the 15th week of 1997.
.. doctest:: relativedelta
>>> datetime(1997,1,1)+relativedelta(day=4, weekday=MO(-1), weeks=+14)
datetime.datetime(1997, 4, 7, 0, 0)
How long ago has the millennium changed?
.. doctest:: relativedelta
:options: +NORMALIZE_WHITESPACE
>>> relativedelta(NOW, date(2001,1,1))
relativedelta(years=+2, months=+8, days=+16,
hours=+20, minutes=+54, seconds=+47, microseconds=+282310)
How old is John?
.. doctest:: relativedelta
:options: +NORMALIZE_WHITESPACE
>>> johnbirthday = datetime(1978, 4, 5, 12, 0)
>>> relativedelta(NOW, johnbirthday)
relativedelta(years=+25, months=+5, days=+12,
hours=+8, minutes=+54, seconds=+47, microseconds=+282310)
It works with dates too.
.. doctest:: relativedelta
>>> relativedelta(TODAY, johnbirthday)
relativedelta(years=+25, months=+5, days=+11, hours=+12)
Obtain today's date using the yearday:
.. doctest:: relativedelta
>>> date(2003, 1, 1)+relativedelta(yearday=260)
datetime.date(2003, 9, 17)
We can use today's date, since yearday should be absolute
in the given year:
.. doctest:: relativedelta
>>> TODAY+relativedelta(yearday=260)
datetime.date(2003, 9, 17)
Last year it should be in the same day:
.. doctest:: relativedelta
>>> date(2002, 1, 1)+relativedelta(yearday=260)
datetime.date(2002, 9, 17)
But not in a leap year:
.. doctest:: relativedelta
>>> date(2000, 1, 1)+relativedelta(yearday=260)
datetime.date(2000, 9, 16)
We can use the non-leap year day to ignore this:
.. doctest:: relativedelta
>>> date(2000, 1, 1)+relativedelta(nlyearday=260)
datetime.date(2000, 9, 17)
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