1.Я занимаюсь по часу в неделю. (по + dative) 2.Я занимаюсь по два часа в день. (по + accusative) Why in the first sentence the dative is used, while in the second it is used the accusative? I don't understand the difference in meaning between the sentences. I'm translating them as: 1.I study an hour per week. 2.I study two hours per day.