django update model doesn't affect auto_now timestamp

It doesn't work as posted in this issue (declared as won't fix) https://code.djangoproject.com/ticket/22981

.update() will only update the fields explicitly passed to it, so datetimefields with auto_now =True aren't updated.

I know the documented behavior is that .update() will ignore updating auto_now[_add] fields as is also confirmed by Yunti's answer. However, for those who wish to force the desired effect - for example, having an auto_now field updated as part of an .update() invocation, the following approach seems to work...

update(field1=val1, field2=val2,..., last_update=datetime.now())

Where last_update is a models.DateTime type field with (or without) auto_now=True. However, note that if you pass some other value to this field other than now() - the current timestamp that is, the ORM doesn't help in correcting this to the current timestamp (which is what the auto_now flag semantics imply). So, for example, in the following snippet, the last_update field does get overridden with the specified timestamp, irrespective of whether it's past, present or future...

    update(field1=val1, field2=val2,..., last_update=datetime.strptime('Jun 1 2005  1:33PM', '%b %d %Y %I:%M%p'))

So, if you wish to enforce the standard semantics of auto_now when making your calls to update(), ensure to correctly pass the current timestamp as the update value to these fields. You are doing it manually (due to a flaw/deficiency in the Django ORM implementation), but you are doing it correctly thus.