When you want to know on what day of the week something happens, the questions to ask are «Когда?» or «В какой день недели?» The day of the week occurs in accusative case after the preposition в. Note that в becomes во before вторник.
| Я работаю в понедельник. | I work on Monday. |
| Я работаю во вторник. | I work on Tuesday. |
| Я работаю в среду. | I work on Wednesday. |
| Я работаю в четверг. | I work on Thursday. |
| Я работаю в пятницу. | I work on Friday. |
| Я работаю в субботу. | I work on Saturday. |
| Я работаю в воскресенье. | I work on Sunday. |
These phrases work as well in the past and future tenses.
| Я работал в понедельник. | I worked on Monday. |
| Я буду работать во вторник. | I will work on Tuesday. |