Question

setings.py:-
    USE_TZ = True
    TIME_ZONE = 'America/Chicago'

class MyModel(models.Model):

        created_at = models.DateTimeField(auto_now_add=True)
        # time zone related field
        user_time_zone = models.CharField(max_length=255, null=True, blank=True)
        time_difference = models.CharField(max_length=255, null=True, blank=True)
        client_date = models.DateTimeField(null=True, blank=True)
        display_date = models.DateTimeField(null=True, blank=True)

MyModel object create

MyModel.objects.create(user_time_zone=form.cleaned_data['prefer_time_zone'])


Signal called after the MyModel is created

def update_time_zone(sender, instance, created, **kwargs):

    if created:

        fmt = "%Y-%m-%d %H:%M:%S %Z%z"

        now_utc = instance.created_at

        if instance.user_time_zone:

            if instance.user_time_zone == 'US/Alaska':

                alaska = now_utc.astimezone(timezone('US/Alaska'))
                print "alaska is_aware", is_aware(alaska)
                print "alaska is_naive", is_naive(alaska)

                instance.client_date = alaska
                instance.display_date = alaska
                instance.time_difference = alaska.strftime(fmt).split(" ")[2]
                instance.save()

                print "alaska now utc", type(now_utc)
                print "alaska type", type(alaska)

                print "alaska", alaska

                # At here i got updated value but when i see inside
                # postgres database value is not updated 

                print "instance.client_date", instance.client_date
                print "us/alaska", alaska.strftime(fmt)

signals.post_save.connect(update_time_zone, sender=MyModel)


instance.created_at = 2016-02-06 21:42:22.552000+00:00
alaska = 2016-02-06 12:42:22.552000-09:00

问题： -

将instance.created_at转换为＆＃39; US / Alaska＆＃39;输出是2016-02-06 12：42：22.552000-09：00。但是当我将client_date和display_date等同于上面的信号中的alaska时，它没有保存我新更新的阿拉斯加值，而是通过添加5小时来更新client_date和display_date by instance.created_at值。我需要通过阿拉斯加时区更新client_date和display_date。

当我调用instance.save（）时，它对postgres数据库没有任何影响。问题是什么？为什么不更新阿拉斯加价值？是否有任何像django强制不更新新值而是使用默认时区更新值？

Answer 1

时区感知日期时间对象.. 00:00:00+00:00和.. 01:00:00+01:00对应于相同的时刻。它们仅以不同方式显示。在Django，a datetime represents a point in time. It’s absolute: it doesn’t depend on anything.

dt = dt.astimezone(whatever_tz)对数据库中的值没有影响。 The database connection’s time zone is set to UTC（USE_TZ=True）。如果您需要保留client_date的时区信息;将它分开存放。

Django日期时间字段未使用时区更新

1 个答案: