its possible to get months between two dates in django queryset?

Question

I'm trying to get make a complete query set, and now all I need is get the months between two DateTime fields from my model, it's possible to do this action in a single query set. Im not talking about filter, cause in the model for example I have two datetimeField() and now what I want to do is, gets months between this dates.

Answer 1

If your database supports DurationField you can go with ExtractMonth:

from django.db import models
from django.db.models.functions import ExtractMonth

queryset = MyModel.objects.annotate(
    diff=models.ExpressionWrapper(
        models.F('date1') - models.F('date2'), output_field=models.DurationField())
    ).annotate(months=ExtractMonth('diff'))

Answer 2

The given answer didn't work for me on postgres because the diff field (DurationField) only support to Extract days function. ExtractMonth return "0".

Here the solution I've found :

queryset = MyModel.objects.annotate(
    months=(ExtractYear("date2") - ExtractYear("date1")) * 12 + (ExtractMonth("date2") - ExtractMonth("date1"))
)

Note that it only consider the difference between the first of each month and not an eventual fractional part given by the days. In this solution 2020-08-12 is considered as the same as 2020-08-01.