Simple. It's one per year, starting in the year you turn 70.5. It's that simple in most cases.
I'll be 70 1/2 in April 2036 (God willing). So that will be the first year I am required to take an RMD. I don't have to take another one in 2036 even though I'd turn 71 later that year. One per year starting with the year in which you turn 70 1/2. That said, we will probably be taking distributions from it before then, but you never know.
Just noticed we were born in the same month and year. Are you still a Libra? (Zodiac Signs NASA Changes Horoscope Dates New Ophiuchus). Apparently I am now a Virgo.