I'm not sure if I understood your question correctly. Russian word for English "day" is "день" (d'en' where apostrophy means softness) If you meant what Russians mean by saying "дай!" (day), it means that they are asking from somebody they are currently talking to to give them something. Дай! is the imperative form of the verb "дать" which means "to give". I hope this helps.

Day - день ! ( for example) Хорошего дня! - Have a nice day!

Thank you

نهار