Your answer is right there in your graph...but it really depends on where your referencing from.
If you're talking about the zero crossing point, it goes just like your graph...
1 going high - 0
3 going low - 60
2 going high - 120
1 going low - 180
3 going high - 240
2 going low - 300
1 going high - 0 (360)

wash-lather-rinse-repeat...