[Django] #36876: Model timestamp fields get different values using auto_now

[Django]

#36876: Model timestamp fields get different values using auto_now
-------------------------------------+-------------------------------------
Reporter: thomax | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: 5.2 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
I have a BaseModel, which I use to set created_at and updated_at. Like so:

{{{
class BaseModel(models.Model):
id = models.CharField(primary_key=True, max_length=50,
default=generate_nanoid, editable=False)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
}}}

When a row is created in one of my tables, both created_at and udpated_at
fields are set. Which is expected. What is ''not'' expected, is that the
created_at field gets a slightly older value than the updated_at field.
Typically:

created_at: 2026-01-22 08:53:38.479806+00
updated_at: 2026-01-22 08:53:38.479828+00

This is, in my opinion, a bug. Because create happens (I presume) in a
single transaction. And also because these fields when, compared for
similiarty, should reveal if the row has been updated at some later time.

As a workaround, one could override the model save method like so:

{{{
def save(self, *args, **kwargs):
"""Ensure created_at and updated_at are identical on creation"""
if self._state.adding:
now = timezone.now()
if not self.created_at:
self.created_at = now
self.updated_at = self.created_at
super().save(*args, **kwargs)
}}}

This should probably get attention because it might be a symptom of
inconsistent timestamp usage during create?

(My exact django version is v5.2.9)
--
Ticket URL: <https://code.djangoproject.com/ticket/36876>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#36876: Model timestamp fields get different values using auto_now
-------------------------------------+-------------------------------------

Reporter: Thomas Drevon | Owner: (none)
Type: Bug | Status: new
Component: Database layer | Version: 5.2
(models, ORM) |
Severity: Normal | Resolution:

Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Description changed by Thomas Drevon:

Old description:

New description:

I have a BaseModel, which I use to set created_at and updated_at. Like so:

{{{
class BaseModel(models.Model):
id = models.CharField(primary_key=True, max_length=50,
default=generate_nanoid, editable=False)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
}}}

When a row is created in one of my tables, both created_at and udpated_at
fields are set. Which is expected. What is ''not'' expected, is that the
created_at field gets a slightly older value than the updated_at field.
Typically:

created_at: 2026-01-22 08:53:38.479806+00
updated_at: 2026-01-22 08:53:38.479828+00

This is, in my opinion, a bug. Because create happens (I presume) in a
single transaction. And also because these fields when, compared for
similiarty, should reveal if the row has been updated at some later time.

As a workaround, one could override the model save method like so:

{{{
def save(self, *args, **kwargs):
"""Ensure created_at and updated_at are identical on creation"""

now = timezone.now()
if self._state.adding:
# On creation, set both to the same timestamp

if not self.created_at:
self.created_at = now
self.updated_at = self.created_at

else:
# On update, only touch updated_at
self.updated_at = now

super().save(*args, **kwargs)
}}}

This should probably get attention because it might be a symptom of
inconsistent timestamp usage during create?

(My exact django version is v5.2.9)

--

--
Ticket URL: <https://code.djangoproject.com/ticket/36876#comment:1>

[Django]

#36876: Model timestamp fields get different values using auto_now
-------------------------------------+-------------------------------------
Reporter: Thomas Drevon | Owner: (none)

Type: Bug | Status: closed

Component: Database layer | Version: 5.2
(models, ORM) |

Severity: Normal | Resolution: invalid
Keywords: auto_now | Triage Stage:

| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Jacob Walls):

* keywords: => auto_now
* resolution: => invalid
* status: new => closed

Comment:

Hi, thanks for the report.

> This is, in my opinion, a bug. Because create happens (I presume) in a
single transaction.

Nothing in the docs yokes this feature to transaction timestamps. If you
need transaction timestamps, `contrib.postgres` ships a `TransactionNow`
expression.

There's also an accepted ticket to remove this feature entirely (#22995),
so implementing model logic for this might be wise anyway.
--
Ticket URL: <https://code.djangoproject.com/ticket/36876#comment:2>