deployment date

please forgive my ignorance on the topic, but does anyone know roughly how far out you get the exact date someone is getting deployed? my older brother is getting deployed again in june, and i was wanting him to be there when i graduate high school, especially because i’ve only seen him three or four times since he joined over ten years ago. i was too young to know anything about the military the first time he got deployed. if anyone knows how far out someone else you know got their date, could you leave it below?