Vitamins in the A.M. or P.M.
It is best to take your vitamins whenever you can best remember to take them - that's more importantly than trying to time it precisely.
More important than the clock is whether to take certain vitamins with a meal or not. For example, multivitamins are best absorbed if taken with food. Iron should also be taken at mealtimes so as not to upset the stomach. Fat soluble vitamins like vitamin E are best taken with a glass of milk, and try to space out calcium dosages throughout the day rather than taking it all at once.