I'd like to add one month to a given date
import datetime
dt = datetime.datetime(year=2014, month=5, day=2)
so I should get
datetime.datetime(year=2014, month=6, day=2)
but with
dt = datetime.datetime(year=2015, month=1, day=31)
I should get
datetime.datetime(year=2015, month=3, day=1)
because there is no 2015-02-31 (and I want my result being round one day after)
Some months have 31 days, some other 30, some 29, some 28 !
so adding a datetime.timedelta
is probably not a good manner of doing (because we don't know the number of days to add)
I noticed that Pandas have an interesting concept of DateOffset
http://pandas.pydata.org/pandas-docs/stable/timeseries.html#dateoffset-objects
but I didn't find a Month
offset, just MonthBegin
or MonthEnd
I see also this post How do I calculate the date six months from the current date using the datetime Python module?
so I tried dateutil.relativedelta
but
from dateutil.relativedelta import relativedelta
datetime.datetime(year=2015, month=1, day=31)+relativedelta(months=1)
returns
datetime.datetime(2015, 2, 28, 0, 0)
so result was rounded one day before.
Is there a (clean) way to round day after ?
edit:
I gave an example with one month to add but I also want to be able to add for example : 2 years and 6 months (using a relativedelta(years=2, months=6)
)
You can use dateutil.relativedelta.relativedelta
and manually check the datetime.day
attribute, if the original day is greater than the new day, then add a day.
The function below accepts a datetime
object and relativedelta
object. Note that the code below only works for years and months, I don't believe it'll work if you use anything below that (days, hours, etc). You could easily modify this function to take years
and months
as arguments and then construct the relativedelta
inside the function itself.
from datetime import datetime
from dateutil.relativedelta import relativedelta
def add_time(d, rd):
day = relativedelta(days=+1)
out = d + rd
if d.day > out.day:
out = out + day
return out
# Check that it "rolls over"
print(add_time(datetime(year=2015, month=1, day=29), relativedelta(years=+4, months=+1))) # 2019-03-01 00:00:00
print(add_time(datetime(year=2015, month=3, day=31), relativedelta(years=+0, months=+2))) # 2015-05-01 00:00:00
# Check that it handles "normal" scenarios
print(add_time(datetime(year=2015, month=6, day=19), relativedelta(months=+1))) # 2015-07-19 00:00:00
print(add_time(datetime(year=2015, month=6, day=30), relativedelta(years=+2, months=+1))) # 2017-07-30 00:00:00
# Check across years
print(add_time(datetime(year=2015, month=12, day=25), relativedelta(months=+1))) # 2016-01-25 00:00:00
# Check leap years
print(add_time(datetime(year=2016, month=1, day=29), relativedelta(years=+4, months=+1))) # 2020-02-29 00:00:00