I see nobody's answered. It doesn't really matter for most people. If it's working, then don't worry about it. Docs differ, and individuals differ in how they react to meds. I've been dosed twice a day, dividing the dose in two, for years. You just find what works best. Some people get stimulated from meds, for example, so the morning is the better time. For those who get very sedated, dividing the dose or taking it at night might work better. It just depends on how you're doing.