I have been dizzy all day long what could be wrong?

Dizziness. Dizziness is a very non specific symptom of many conditions from poor diet, diabetes and nerve (neurologic) conditions. Don't try to self diagnosed. See a doctor at the earliest possible!
Very vague. Dizziness is a very vague term. You could be having problems with low blood pressure, an infection in your ears, you could be having a seizure. You need to be evaluated by your doc to track down the cause.