There is an option called "use seconds", but the edit template unfortunately does not cover that checkbox function so we get a missing data error.
In admin2 design (other designs not tested):
1) create a new class or edit a existing one
2) add ezdatetime attribute
3) set it to REQUIRED
4) check the checkbox "use seconds"
5) create a object of that class
6) fill out all information of ezdatetime attribute (you will see already that the input field for the seconds is missing)
7) send for publishing
=> The draft could not be stored.
Required data is either missing or is invalid:
- new attribute6: Missing datetime input.