How do I change my menstruation dates?

I will have to travel in August and the dates coincide with my menstruation for the moment. I have noticed that my menstruation dates have shifted through the years and months because of periods of stress. Is it possible to shift voluntarily my menstraution from the middle of the month to the end of the month? I don't want to take pills. Some say vitamin C but I hear that it just postopones for day or two. I want to shift the dates like the shift without me wanting to.