Hello,

I think in the task's calender the field date_deadline is used. and the type of this field is date. So you can change the type

of this field to datetime.

Hope this could help

Qutechs, Ahmed M.Elmubarak's answer was relevant but on odoo11 we can not change the date of date_deadline from date to date / time. The system returns an error:

 × Odoo server error - Warning The properties of the database fields can not be modified in this way! Modify them via Python code, preferably via a custom module! 

Hi , using V10 and V11 , the default behavior of the Project Task "Calendar View" is ALL DAY , so you have to make changes to the calendar view and it works for me and i have posted the How to in my Blog and you can take a look , thanks.

https://wp.me/p8iOGA-7FZ , How to  make Odoo Project Task to respond to time specific instead of All day?

Kalmen

Yes you are right. so I change to "date_start" and add "date_end". I take this value from gant view. But doesn't work