Learning the basic vocabulary of the Russian language, you have learned to speak about time - to ask and answer what time it is, describe different periods of time from a second to a century. In one of the articles on this website we analyze, which grammar structures to use, in order to answer the question "Когда?" (When?), and which prepositions and cases to use for this purpose. In this article I am going to tell you, that there are the structures in Russian with the prepositions ЧЕРЕЗ and ПОСЛЕ for the time description. They are differed by a context and the word describing time period. Thus, if we want to denote action which is followed by some event (that we also mention), we use the structure: preposition ЧЕРЕЗ + accusative case (words "минута" - minute, "час" - hour, "день" - day, etc.) or ПОСЛЕ + genitive case (nouns which describe any events and phenomena).
Наш рейс через три дня - Our flight will be in three days.
Через минуту приедет такси - Taxi will come in a minute.
После грозы пахнет свежестью - There is fresh air after a storm.
После визита врача я почувствовал себя намного лучше - I felt myself better after my doctor's visit.
To describe time, when one action or event has taken place before another mentioned action or event, we use the structure: preposition ДО + genitive case. To describe the event which has taken place a moment before another mentioned event takes place, we use the structure: preposition ПЕРЕД + instrumental case.
До завтрака мы успели сделать уроки - We did homework before breakfast.
Магазин работает до девяти часов - The store works till 9 o'clock.
Перед приходом гостей нужно сделать уборку - One needs to clean house before guests' visit.
Перед фильмом всегда показывают рекламу - They always show advertisement before a movie.