Example form is linked to a database table, but won't be saved in this example.
When you submit the form, the value is presented with debug_dump(), so strings are quoted and array values listed.
<?php
$field = new form_field_time($form, 'Time');
$field->db_field_set('time');
$field->invalid_error_set('Your time does not appear to be correct.');
$field->required_error_set('Your time is required.');
$field->min_time_set('Your time has to be after 3am.', '03:00');
$field->max_time_set('Your time cannot be set in the future.', time());
?>