Add support for months and years in INTERVAL field of PostgreSQL

[None]

PostgeSQL supports months and years in INTERVAL field, but django doesn't support it.
I propose add new field postgres.IntervalField that supports months and years by using python-dateutil python library.

[Tim Graham]

What's the reason DurationField doesn't support it? How soon do we overflow the bigint storage of other database backends?

[None]

I propose add special for PosgreSQL field, that will be using INTERVAL full.

Month is not a static value and you can't convert it to bigint.
For example:

TIMESTAMP '2001-02-02' + INTERVAL '1 month' = TIMESTAMP '2001-03-02'
TIMESTAMP '2001-02-02' + INTERVAL '31' days' = TIMESTAMP '2001-03-05'

In python you must to use python-dateutil:

>>> datetime(2015, 1, 31) + relativedelta(months=1)
datetime.datetime(2015, 2, 28, 0, 0)
>>> datetime(2012, 2, 29) + relativedelta(months=12)
datetime.datetime(2013, 2, 28, 0, 0)

[Marc Tamlyn]

Support for non-fixed durations is complicated - As liminspace mentioned Python's timedelta does not support months or years (see ​https://docs.python.org/3.2/library/datetime.html#datetime.timedelta). Oracle actually has two completely separate fields for them, and the other databases we could not store it in a single column either.

Also, what is the form field representation? How do we anticipate a user will specify "2 months, 4 days and 1 hour" (in every language?), and will they understand that 30 days != 1 month? In fact in postgres depending on which functions you use to calculate age, you either get calendar months or 30 day "months".

I think this should be possible as an external field for postgres and/or Oracle, as it has external python dependencies as well it should live as an external package. I'm not sure what psycopg2 does for month/year based durations as normally it will try to cast interval to a timedelta.