Learn Russian: Ему надо записаться на осмотр через месяц. - He needs to make an appointment for a check-up in a month.

In Russian, when you want to say that something will happen "in" a certain amount of time from now (like "in a month" or "in an hour"), you use the preposition через followed by the Accusative case. Using в would mean something else entirely, like an action happening during a specific month. Since месяц (month) is a masculine inanimate noun, its Accusative form looks exactly the same as its dictionary form.

Why does the sentence start with Ему (to him) instead of Он (he)?

The word надо (needs / it is necessary) requires the person who needs something to be in the Dative case. So, "He needs" translates literally to "To him it is necessary" (Ему надо). This is a very common structure you will see with words expressing need, feeling, or age.

Why use the reflexive verb записаться instead of just записать?

The non-reflexive verb записать means to write an object down or record it (like a phone number). By adding the reflexive ending -ся, записаться literally means "to write oneself down" or "to sign oneself up." This is the standard Russian way to say "to make an appointment."

Why do we use на осмотр to say "for a check-up"?