Why are DateTimeField auto_now and auto_now_add bad?

[Mattias Linnap]

Hi all,

I've seen DateTimeField's auto_now and auto_now_add parameters often described as "buggy" or "error-prone". For example:

https://code.djangoproject.com/ticket/22995

https://groups.google.com/forum/#!topic/django-developers/TNYxwiXLTlI

The ticket proposes to document these downsides or problems in more detail. But until that happens, is there a blog post or mailing list post somewhere that summarises the gotchas to watch out for with auto_now?

Thanks,

Mattias

[Russell Keith-Magee]

I'm not aware of a formally documented list anywhere. 

To the best my knowledge, the bug/downside that is referred to here is that the fields *won't* automatically update in *every* circumstance. You need to actually *save* the model to make the field update. Calls to update, save_base, etc won't invoke the "auto" part of the field logic, and the timestamp won't be adjusted.

Yours,

Russ Magee %-)

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[cmawe...@gmail.com]

It gets confusing if those fields are editable in the admin. I recommend setting editable=False on those fields.