Time expressions with через, за and на + accusative (через час, за неделю, на месяц)

Поезд отходит через десять минут. Мы едем на море на неделю. Я прочитал эту книгу за два дня, а вчера читал её весь вечер.The train leaves in ten minutes. We are going to the sea for a week. I read this book in two days, and yesterday I read it all evening.

Three small prepositions answer three different questions about time, and all of them are followed by the accusative of a period of time (without a numeral; after a numeral the noun follows the numeral pattern, as shown below): через (in … / after …), за (in … = how long it takes to finish something) and на (for … = a planned period). A plain period of time without a preposition (два часа, всю неделю) answers "for how long did it last?". The accusative itself is covered in The Russian accusative case: inanimate objects. Days, months and dates are in Days, dates and time expressions in Russian, and the clock is in Telling the time in Russian.

In short: через час (in an hour), за час (in the course of an hour, to finish something), на час (for an hour, planned), час (for an hour, how long it went on), час назад (an hour ago).

The period of time in the accusative

Without a numeral, the word for a period of time stands in the accusative in every pattern below. Most of these nouns are inanimate, so masculine nouns look like the nominative, and only the feminine ending changes:

After a numeral, the noun follows the usual pattern from Russian nouns after numbers: через час, через два часа, через пять часов; за неделю, за две недели, за пять недель.

через: in … time / … later

The preposition через says how much time must pass before something happens. It counts forward from the moment of speaking, or from a moment in the story:

• Урок начнётся через пять минут. (The lesson will start in five minutes.)
• Я позвоню тебе через час. (I will call you in an hour.)
• Мы увидимся через неделю. (We will see each other in a week.)
• Он вернулся через год. (He came back a year later.)

For the past, через can mean "after" a period from some earlier moment: Я приехал в Москву, а через месяц нашёл работу. (I came to Moscow, and a month later I found a job.)

за: how long it takes

The preposition за says in how much time something was, or will be, completed. It goes with an action that has a result and usually with the perfective aspect, as in Aspect in the Russian past tense:

• Я прочитал эту книгу за два дня. (I read this book in two days.)
• Она сделала домашнее задание за час. (She did her homework in an hour.)
• Мы дойдём до парка за десять минут. (We will walk to the park in ten minutes.)

It answers "in how much time did you manage to do it?", so it does not describe a state that simply went on (Мы жили там год — not за год).

на: for a planned period

The preposition на says for how long something is meant to be, usually after a verb of going, leaving, giving or renting. It points to the plan or the result, not to what actually happened:

• Мы едем на море на неделю. (We are going to the sea for a week.)
• Я взял книгу на три дня. (I took the book for three days.)
• Они сняли квартиру на год. (They rented a flat for a year.)
• Он уехал на месяц. (He went away for a month.)

No preposition: how long it lasted

To say how long an action or a state went on, put the period straight into the accusative. This is the usual pattern for ongoing, repeated or unbounded actions (often with the imperfective, though a perfective such as Он проработал там два года can also take it), and it is the one to use for "all day" and "all week" with весь, вся, всё, which agree with the noun:

• Мы жили в Москве три года. (We lived in Moscow for three years.)
• Я читал книгу два часа. (I read the book for two hours.)
• Она работала весь день и всю неделю. (She worked all day and all week.)
• Вчера мы гуляли весь вечер. (Yesterday we walked all evening.)

The same accusative also says how long something goes on regularly: Я занимаюсь русским два часа каждый день. (I study Russian for two hours every day.)

назад: ago

The word назад comes after the period of time and says how long ago something happened:

• Я видел его два часа назад. (I saw him two hours ago.)
• Они переехали сюда год назад. (They moved here a year ago.)
• Это было много лет назад. (That was many years ago.)

Common mistakes

• ❌ Я приеду через неделя. → ✅ Я приеду через неделю. (The period after через is in the accusative: неделя → неделю)
• ❌ Мы жили в Москве за три года. → ✅ Мы жили в Москве три года. (A state that went on takes the bare accusative; за is for completing something)
• ❌ Мы жили в Москве на год. → ✅ Мы жили в Москве год. (На is for a planned period, not for how long something lasted)
• ❌ Он прочитал книгу в два дня. → ✅ Он прочитал книгу за два дня. (To finish something within a period, use за)
• ❌ Я видел его назад два часа. → ✅ Я видел его два часа назад. (Назад comes after the period)
• ❌ Я работал весь неделю. → ✅ Я работал всю неделю. (Весь agrees with the noun: неделя is feminine)

Quick check

Which preposition or form fits each gap?

1. Поезд отходит ____ десять минут. (The train leaves in ten minutes.)
2. Он прочитал всю книгу ____ два дня. (He read the whole book in two days.)
3. Мы едем на море ____ неделю. (We are going to the sea for a week.)
4. Она работала ____ день. (She worked all day.)
5. Я видел его два часа ____. (I saw him two hours ago.)
6. Он вернётся через ____. (He will be back in a week.)

Key takeaways

• через + accusative says when something will happen (через час) or happened a period later (через месяц).
• за + accusative says how long it takes to finish something (за два дня), usually with the perfective.
• на + accusative says for how long something is planned (на неделю), often after a verb of going, leaving, giving or renting.
• A bare accusative says how long an action or a state went on (три года, весь день); весь agrees with the noun.
• назад comes after the period: два часа назад.
• Only the feminine nouns change in the accusative: неделя → неделю, минута → минуту.