The time field type should be a TIME type in your database.
'start_time' => array(
'type' => 'time',
'title' => 'Start Time',
'time_format' => 'HH:mm', //optional, will default to this value
)
In the edit form, an admin user will be presented with a jQuery timepicker.
The time_format option lets you define how the time is displayed. This uses the formatting options from jQuery timepicker.
The time field filter comes with a start and end time. This allows you to narrow down the result set to a range, set only a minimum time, or set only a maximum time.