id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37013	Omitting tzinfo argument to Trunc & Extract with USE_TZ = True and TIME_ZONE != UTC creates ambiguity for migrations	Jacob Walls		"The `Trunc()` and `Extract()` database functions apply timezone conversions if `USE_TZ = True`. When the `tzinfo` argument is omitted, the timezone is inferred from `settings.TIME_ZONE`. If these functions are used in a `db_default` expression, this information is not captured by migrations, meaning that if `settings.TIME_ZONE` changes over the life of a project, then the database may never receive a corresponding update.

{{{#!py
from django.db import models
from django.db.models.functions import ExtractHour, Now

class Person(models.Model):
    hour = models.IntegerField(db_default=ExtractHour(Now()))
}}}

To reproduce:
- Change `settings.TIME_ZONE` to ""America/Chicago"".
- Make migrations, notice no migration generated.
- Emulating the database-default python-side (as SQLite must do sometimes, see rest of linked forum post) now no longer produces the same value as the database.

In this [https://forum.djangoproject.com/t/extract-isnt-safe-to-use-in-db-default-on-sqlite-if-time-zone-changes-at-some-point/44781/6 forum reply], there was an idea to implement `Trunc/Extract.deconstruct()` to deprecate omitting `tzinfo` if serialized into a migration and eventually make it default to `get_current_timezone()` when not provided."	Bug	new	Database layer (models, ORM)	6.0	Normal		tzinfo, TIME_ZONE		Unreviewed	0	0	0	0	0	0