Actually, the date field is nothing more than a text field with a label. It is outside. What you get when using this field from a date module is a big date check to make sure what the user typed / selected makes sense. Another thing you get is various javascript tools that help print the actual date. But for this you need a data module.
Since time is much simpler (universal) than date, you don't need a lot of checking. So, all you need to turn it into a fantasy time field is to add some javascript to help, but it really is not necessary.
So, the short answer is no, you can't do something like that, but you don't need either. You can create your own hook_elements () time field, though, if you really wanted to.
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