Date fields with time support

no, it is not possible.

Default is only dates because ProjeQtOr does not plan on an hourly basis, but only on a daily basis.
This means that if two activities are planned on the same day, you don't know which is planned first... because none is planned first

For start and end dates, in most cases (for activities) they are automatically updated from real work values.
But real work allocation does not provide information on hours of start / end work on an item, so it would not be possible to set hours.

For Tickets, the way to set start and end are different, and it may be important to check some indicators based on hourly durations.
So start and end dates for tickets are timestamps.

If you wish to have time on specific start / end for some items, please express it explicitly.
It won't be generalized.

Will be good to have a time format option as well...

what do you mean ?

Date formating uses Dojo framework internationalization module, through the use of dojo.dateText widget.
So display is automatically adapted to the locale of the browser.