As far as i can research, we can use this as alternative solution:

1. Change the field from `Datetime` to `Float`:
your_field = fields.Float(string='Your Field')

2. Then, in the form view, add `widget="float_time"`:

With this, there's no popup to show (It's bad, i know).

But as i mentioned before, this solution is just a alternative solution until we find better solution.

Other answers are welcome.

Note for the report view or email view, we can use this: 

t-options="{'widget': 'float_time'}"

Thanks.

Hi,

If you need to change the date time format everywhere inside the database, you can change it from language.

See: https://www.youtube.com/watch?v=Cl6DiqJnM8M

Thanks