About once a year, i have one day when i'm dizzy all day. vertigo, i think. why could this be? how could i prevent or deal with it?

Yearly dizzy spell: If your dizziness is once a year, have you checked your blood pressure when you are dizzy? Low blood pressure and you get dehydrated for some reason, you could become dizzy. That could also happen with sleep deprivation. Benign positional vertigo is usually related to body position, but can sometimes, rarely, recur. Have you seen your family doctor or an ear, nose and throat specialist?