Wikipedia has an article on the calendar¹, including how and why the movable feasts are calculated.
¹ https://en.m.wikipedia.org/wiki/Eastern_Orthodox_Church_litu...
Wikipedia has an article on the calendar¹, including how and why the movable feasts are calculated.
¹ https://en.m.wikipedia.org/wiki/Eastern_Orthodox_Church_litu...
This is further reinforced by January, 7 being a state holiday in Russia - defined directly like that, without any references to the old calendar.
It's an interesting question as to what exactly is going to happen when it's time to move it. As I noted earlier, the Russian law on state holidays explicitly designates January, 7 as Christmas - so that would need to be amended to conform to what the Church says. But, much like in the West, Christmas is not a purely religious holiday in Russia - it's effectively the last day of the New Year holiday week. In theory, individual regions can opt out of it (to reflect their local religious traditions - some are majority Muslim or Buddhist), but none have done that in practice. So, if the question of moving it arises, it will be debated by the society at large, not only by the Orthodox.
Thus, most believers aren't aware of those details even if they self-identify as Orthodox Christian.