There is a 'duration' field available (if you mean "time" as in "amount of time" rather than "time of day").
Other than that, you can either create a "group" with an hour + minute selector elements within it, or you can make a custom field type (based on the date + time selector) and use that (if you go down that route, make sure you call the MoodleQuickForm::registerElementType() function to let Moodle know about your custom field type).
Other than that, you can either create a "group" with an hour + minute selector elements within it, or you can make a custom field type (based on the date + time selector) and use that (if you go down that route, make sure you call the MoodleQuickForm::registerElementType() function to let Moodle know about your custom field type).