Django default=timezone.now() saves records using "old" time
Question:
This issue has been occurring on and off for a few weeks now, and it’s unlike any that has come up with my project.
Two of the models that are used have a timestamp field, which is by default set to timezone.now().
This is the sequence that raises error flags:
-
Model one is created at time 7:30 PM
-
Model two is created at time 10:00 PM, but in the
MySQL database it’s stored as 7:30 PM!
Every model that is created
has its time stamp saved under 7:30 PM, not the actual time, until a certain
duration passes. Then a new time is set and all the following models
have that new time… Bizzare
Some extra details which may help in discovering the issue:
I have a bunch of methods that I use to strip my timezones of their tzinfo‘s and replace them with UTC.
This is because I’m doing a timezone.now() - creationTime calculation to create a: “model was posted this long ago” feature
in the project. However, this really should not be the cause of the problem.
I don’t think using datetime.datetime.now() will make any difference either.
Anyway, thanks for the help!
Answers:
Just ran into this last week for a field that had default=date.today(). If you remove the parentheses (in this case, try default=timezone.now) then you’re passing a callable to the model and it will be called each time a new instance is saved. With the parentheses, it’s only being called once when models.py loads.
Just set the parameter auto_now_add like this.
timestamp = models.DateTimeField(auto_now_add=True)
Update:
Please don’t use auto_now_add. It is not the recommended way, instead do this:
from django.utils import timezone
timestamp = models.DateTimeField(default=timezone.now)
This issue has been occurring on and off for a few weeks now, and it’s unlike any that has come up with my project.
Two of the models that are used have a timestamp field, which is by default set to timezone.now().
This is the sequence that raises error flags:
-
Model one is created at time 7:30 PM
-
Model two is created at time 10:00 PM, but in the
MySQL database it’s stored as 7:30 PM!
Every model that is created
has its time stamp saved under 7:30 PM, not the actual time, until a certain
duration passes. Then a new time is set and all the following models
have that new time… Bizzare
Some extra details which may help in discovering the issue:
I have a bunch of methods that I use to strip my timezones of their tzinfo‘s and replace them with UTC.
This is because I’m doing a timezone.now() - creationTime calculation to create a: “model was posted this long ago” feature
in the project. However, this really should not be the cause of the problem.
I don’t think using datetime.datetime.now() will make any difference either.
Anyway, thanks for the help!
Just ran into this last week for a field that had default=date.today(). If you remove the parentheses (in this case, try default=timezone.now) then you’re passing a callable to the model and it will be called each time a new instance is saved. With the parentheses, it’s only being called once when models.py loads.
Just set the parameter auto_now_add like this.
timestamp = models.DateTimeField(auto_now_add=True)
Update:
Please don’t use auto_now_add. It is not the recommended way, instead do this:
from django.utils import timezone
timestamp = models.DateTimeField(default=timezone.now)