How long ago, about, did music begin to be written down?

The earliest written form of music is known to us from the Babylonian period which written in cuneiform tablet about 1400 B.C. Later on, we found music notation from Ancient Greece, which shows compositions and fragments of music. The modern written music which we know today is related to the 1200s Gregorian Chants in the church.        

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.