Soldato
Hristos se rodi to all my fellow Orthodox Christians on this most Wonderful Christmas Day.
Some Othodox Christian churches celebrate on the 7th rather than the 25th because they still use the Julian Calendar. Russia is one of these.
Gregorian Calendar I believe you will find
Although there is still debate over whether it's the 6th or 7th between the various branches of Orthodoxy but we won't get into that it's rather complicated.
The OP is speaking Serbian who also celebrate today.
Gregorian Calendar I believe you will find
Sounds like Christ from Joy in Russian. My wife's uncle is Orthodox and wouldn't have lunch with us on Christmas day.
It's "Christ Is Born" in Serbian
the traditional reply would be Vaistinu se Rodi (Ваистину се роди) - "It is true, he has been born."