How can I subtract or add 100 years to a datetime field in the database in Django?

python django datetime django-database
kelvinfix picture kelvinfix · May 3, 2011 · Viewed 56.6k times · Source

How can I subtract or add 100 years to a datetime field in the database in Django?

The date is in database, I just want to directly update the field without retrieving it out to calculate and then insert.

Answer

Max picture Max · May 3, 2011

I would use the relativedelta function of the dateutil.relativedelta package, which will give you are more accurate 'n-years ago' calculation:

from dateutil.relativedelta import relativedelta
import datetime

years_ago = datetime.datetime.now() - relativedelta(years=5)

Then simply update the date field as others have shown here.

Related questions

Django auto_now and auto_now_add

For Django 1.1. I have this in my models.py: class User(models.Model): created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) When updating a row I get: [Sun Nov 15 02:18:12 2009] [error] /home/ptarjan/projects/twitter-meme/django/…

Read More
How can I filter a date of a DateTimeField in Django?

I am trying to filter a DateTimeField comparing with a date. I mean: MyObject.objects.filter(datetime_attr=datetime.date(2009,8,22)) I get an empty queryset list as an answer because (I think) I am not considering time, but I want "…

Read More
Can't compare naive and aware datetime.now() <= challenge.datetime_end

I am trying to compare the current date and time with dates and times specified in models using comparison operators: if challenge.datetime_start <= datetime.now() <= challenge.datetime_end: The script errors out with: TypeError: can't compare offset-naive …

Read More