Answer My Searches

Update: Here’s the best way:
download and install the python-dateutil package from http://labix.org/python-dateutil

From the examples on the page here’s the code you would use:

import datetime
from dateutil.relativedelta import relativedelta

NOW = datetime.datetime.now()
NOW + relativedelta(months=+1)

Below is my old, home-brewed method (does seem to work):

You’ll need the mxDateTime module to run it.

import datetime
import mx.DateTime
from math import ceil

def monthify(anint):
    if anint%12==0:return 12
    else:return anint%12

def add_months_to_date(base_date,number_months):
    """Note: if day in base_date is > highest day in new month
    then day become highest day in new month.
    base_date can be a datetime.date,datetime.datetime,
    or mx.DateTime.Date.  We return datetime.datetime"""
    base_date=mx.DateTime.Date(base_date.year,base_date.month,base_date.day)
    #calculate what year it will be
    years_to_add=ceil(
        float((number_months-(12-base_date.month)))/float(12))
    newyear=base_date.year+max(years_to_add,0)
    #calculate new month
    newmonth=monthify(base_date.month+number_months)
    #calculate new day
    max_day=mx.DateTime.Date(newyear,newmonth,1).days_in_month
    newday=min(base_date.day,max_day)
    #finish up
    #new_date=mx.DateTime.Date(newyear,newmonth,newday)
    new_date=datetime.datetime(newyear,newmonth,newday)
    return new_date

if __name__=="__main__":
    #some testing
    print add_months_to_date(datetime.date(1999,12,31),2)
    print add_months_to_date(datetime.date(1999,12,1),1)
    print add_months_to_date(datetime.date(1999,12,1),31)
    print add_months_to_date(datetime.datetime(2020,1,1),4)
    print add_months_to_date(datetime.datetime(2005,5,3),1)
    print add_months_to_date(datetime.datetime(2006,7,27),15)

Update

I have now created this online date calculator to let you add months to a date and more. You can also view its Python source code to see how it works.