When the field is configured to display both date and time components, the client fails to render the native Date/Time UI picker widget, instead degrading the control into a standard text input field. This creates a poor user experience and introduces a high risk of data entry errors, as users are forced to manually type date and time strings without the aid of the standard picker widget or validation formatting. The property of the field give the impression that it can display BOTH Date and Time.
In the Date/Time field's property - first tab (Field Info), enable "Calendar/Time Control".
In the Date/Time field's property - second tab Control), enable "Display Date".
Preview the form in Notes Client, notice that Date picker is enabled (this is expected result).
Go back to Domino Designer > Date/Time field's property - second tab Control), enable "Display Time" and disable "Display Date".
Preview the form in Notes Client, notice that Time picker is enabled (this is expected result).
Go back to Domino Designer > Date/Time field's property - second tab Control), enable both "Display Time" and "Display Date".
Preview the form in Notes Client, notice that date/time field was converted to standard text input.
This is solved by displaying separate fields for date and time, and possibly also for time zone, in edit mode. This is how the calendar in a standard mail database solves this. But for ease of use, it should be possible to set the date and time selection for a single field.