When (on what date) …?

What is the right way to say?
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- КОГДА БУДЕТ КОНФЕРЕНЦИЯ?

- …

  1. ПЕРВЫЙ МАРТ
  2. ПЕРВОЕ МАРТА
  3. ПЕРВОГО МАРТА
  4. МАРТ, ОДИН

Not sure?

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- Когда будет конференция?

- Первого марта.

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ЧИСЛО – когда? => ПАДЕЖ №2

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When we speak about time (когда … ? – when … ?), the form of a noun depends on its meaning. If it’s a date (число), we use Genitive case (падеж 2) without preposition.

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1. The noun “число” (date) itself is absent in the phrase but it is implied.
2. We use adjective “первый” and not the numeral “один” because we indicate what (какой) date it is and not how many (сколько) dates.
3. The adjective “первый” takes the form of Genitive case neuter (падеж 2, оно), because it qualifies the implied noun “число” (оно, date). Genitive neuter of “первый” is “первого”.
4. The word “март” is used in Genetive case (падеж 2) because noun+noun combination requires the “падеж 2″ form of the second noun. Genitive of “март” is “марта”.

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