[Django] #27306: Document relation between auto_now/auto_now_add and timezones
Django
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Reporter: Baptiste Mispelon | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Documentation | Version: 1.10
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 |
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The documentation for `DateField.auto_now` states: "Automatically set the
field to now every time the object is saved." [1]
It achieves this by doing `value = datetime.date.today()`. However, as
noted in the discussion on #27082 and #25181 this might not exactly be
"now" (depending on what you think "now" means).
I think the documentation should clarify how `auto_now` interracts with
timezone settings, and in particular what we mean when we say "now". I
also think there's a bug lurking in the usage of `datetime.date.today()`
and we should use the new `timezone.localdate()` instead.
[1]
https://docs.djangoproject.com/en/1.10/ref/models/fields/#django.db.models.DateField.auto_now
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Ticket URL: <https://code.djangoproject.com/ticket/27306>
Django <https://code.djangoproject.com/>
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Django
Reporter: Baptiste Mispelon | Owner: nobody
Cleanup/optimization |
Component: Documentation | Version: 1.10
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
Comment (by Aymeric Augustin):
The current behavior is consistent with how Django handles time zones.
When the ORM must make a guess, it uses the default time zone, and that's
what happens here.
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Ticket URL: <https://code.djangoproject.com/ticket/27306#comment:1>
Django
Reporter: Baptiste Mispelon | Owner: nobody
Cleanup/optimization |
Component: Documentation | Version: 1.10
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
Comment (by Baptiste Mispelon):
Here's how our date/time-related fields handle `auto_now*`:
* `DateField` uses `datetime.date.today()`: today's date in the default
timezone
* `TimeField` uses `datetime.datetime.now().time()`: the clock time in the
default timezone
* `DateTimeField` uses `timezone.now()`: the current datetime in the
current timezone
("current" and "default" timezone are defined here:
https://docs.djangoproject.com/en/1.10/topics/i18n/timezones/#default-
time-zone-and-current-time-zone).
As Aymeric said, there's no bug here so this is only a documentation
issue: we should clarify what "now" and "today" mean for `auto_now`.
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Ticket URL: <https://code.djangoproject.com/ticket/27306#comment:2>
Django
Reporter: Baptiste Mispelon | Owner: nobody
Cleanup/optimization |
Component: Documentation | Version: 1.10
Severity: Normal | Resolution: invalid
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Baptiste Mispelon):
* status: new => closed
* resolution: => invalid
Comment:
Turns out this is already documented in a "note" paragraph just under.
I should have read the documentation all the way through, sorry for the
noise :(
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Ticket URL: <https://code.djangoproject.com/ticket/27306#comment:3>
Django
Reporter: Baptiste Mispelon | Owner: nobody
Cleanup/optimization |
Component: Documentation | Version: 1.10
Severity: Normal | Resolution: invalid
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Aymeric Augustin):
Small correction: `timezone.now()` is the current date and time in UTC,
but that's irrelevant anyway: an aware datetime value will be stored
correctly and can be converted in any timezone, so it doesn't matter what
time zone the auto default value is generated in.
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Ticket URL: <https://code.djangoproject.com/ticket/27306#comment:4>