I think that's the whole point, to be in synch, that is. However, I think that just as there is a divine design in balance with nature it permeates everything. We have 12 zodiac signs that are broken up into 4 elements. Some people need to be earth signs, some water, air, fire - therein lies balance. I bled on the new moon for years. I bled on the full moon for some time and now I seem to be back to the new moon. Perhaps some are meant to bleed on the full and some on the new. Remember, menstrual blood is the only blood that is let from peace. As women, we transmute and cleanse for everyone, effectively, by our tithing of menstrual blood once a month. It is a divine ritual. If all of us bled on the full moon - what Goddess would help transmute our prayers on the new moon? It'd be imbalanced.