Viacheslav’s name day is September 28, the feast of Wenceslaus of Bohemia.
Churches that follow the Old (Julian) Calendar keep the same feast on October 11 of the civil calendar. See everything commemorated on September 28.
The saint behind the name
Wenceslaus of Bohemia
September 28, Martyr, Βιατσεσλάβος
St. Wenceslaus was raised by his grandmother St. Ludmila and became prince of Bohemia while still young, ruling with justice, building churches, and caring for the poor with his own hands. His pagan-minded brother Boleslav, envying his rule and hating his faith, invited him to a feast and killed him at the church door in 935.
Name days: Wenceslaus, Wenceslas, Vaclav, Vyacheslav, Viacheslav
Also celebrating on September 28
These names share the feast, many of them other forms of the same name:
Wenceslaus, Wenceslas, Vaclav, Vyacheslav
What to say on a name day
The Greek wish is Χρόνια Πολλά (Chronia Polla), “many years.” A call or a short message on the day is what people remember. See name day wishes you can send and what a name day is.