Django naming conventions for dates

Indeed, as far as I can tell there's no canonical convention for Django, but I really like the Rails convention (which I suppose also inspired Symphony):

• created_at for DateTime fields
• created_on for Date fields

created works fine for creation dates, but as soon as you have more ambiguous fields like activated, it becomes a problem. Is it a boolean or a date/datetime? Naming conventions exist to help developers understand code faster and waste less time with unimportant decisions. That's the philosophy behind the Convention over Configuration paradigm, which is big in the Rails community but not as much in Django's unfortunately. This confusion I mentioned for example is typical and that's why I prefer to always be extra clear:

• If it's a boolean is_activated
• If it's datetime activated_at
• If it's just a date activated_on

I've heard people say that "you shouldn't mix field names with data types" but it seems like a rather empty tip in my opinion and I've never heard any concrete argument behind it. If we want to optimize code readability and decision making then I really think explicit naming conventions are the way to go.