In Russia of course, during Tatiana's lifetime, the difference in dates between the calendars didn't mean anything. As far as she was concerned her birthday was (and is) May 29. The Communists brought in the Western Calendar, which is, for the most part unsuitable for Orthodox Christianity as it gets everything out of synch. In Orthodox countries where they use the 'new' calendar they have fixed date Feasts like Christmas on the new style, but all moveable Easter related ones on the Old calendar. It creates all kinds of problems. For example, it can mean the Fast of the Apostles ends up being minus two weeks! (That is because the start of the Fast is dependent on the date of Pentecost which in turn is dependent on the date of Easter, but the date for the end of the Fast is unchanging - the Day of Sts Peter and Paul).
To my mind, the best solution is that which we see these days in the Russian, Japanese, Serbian etc Orthodox Churches where ecclesiastic dates are all according to the old calendar, but civil dates are on the new. Thus Christmas is celebrated on the Church date of December 25, which corresponds to the civil date of January 7.