I have a book listing various saints (of the Roman Catholic Church, not the Russian Orthodox) and it only lists one St. Tatiana. It says that this saint died around the year 230 and was martyred in Rome during the reign of the Emperor Severus. It then states that this date "also honors the saint Tatiana, venerated by the Greek Orthodox Church, with Mertios and Euthasia."
Both feast days are given as January 12.
Does anyone know if this was in fact the feast day of GD Tatiana? Does anyone know anything about the Eastern Orthodox St. Tatiana?