Orthodox Easter varies. Sometimes it coincides with Western, and sometimes it’s one, or two, weeks different. It’s because Easter doesn’t have a fixed date, but is calculated by the phases of the moon.
As time goes by the two calendars will get further and further apart, and Eastern and Western Easter will nover coincide. I saw somewhere that this would occur in the 27th century, but I may be misremembering.
Not a problem, because
The difference grows 3 days every 400 years, or 15 days in 2000 years, and with the difference now being 13 days, it would be more like 3700 AD , another 1700 years, before the difference grows to be a full moon cycle, 29 days, and hence the Easters won’t coincide.
The common calander Easter is ecclesiastic Easter. Someone just says what days Easter will be, based on a model of the moon cycles… you know, like your almanac … Rather than having people trying to observe the moon and having an argument about what day the full moon will fall on, what in the month before easter ? how can a calander be printed years in advance if they are still arguing the month before… so with the model, they can state the date for Easter far into the future and print calanders… who decides ? how far into the future has the date for easter been declared ? and is it the proper way, why not just lock in one specific date for Easter like Christmas … ?
1752 in the UK, and it caused a riot or two among the know-nothings who demanded “Give us back our eleven days!”
I think the Orthodox also use a slightly different calculation for Easter.
Their definition is the same - Easter is the first Sunday after the first full moon in spring (i.e., on or after 21 March). It’s just that the Orthodox have a different reckoning of when spring begins, and hence the same definition will (usually, though not inevitably) lead to a different result.
There is an added line in the calculation that states: can not come before or coincide with Passover.
Confirmed by this very non-practicing-but-raised-Catholic who is taking the tree down right now 
The difference (between the Gregorian calendar and the actual rotation of the Earth around the Sun) grows by one day in 3,200 years - after that period, the Gregorian rule has omitted 24 leap days, but on the basis of the 128-year cycle should have omitted 25. This can fairly easily be dealt with by means of an ad hoc adjustment of a day around the year 4782. It might be a nuisance but buys us another three millennia before the problem occurs again.
Here, the festive season runs from Halloween to Super Bowl Sunday. 
It’s not that Orthodox say Christmas is on January 7. Orthodox Christmas is on December 25, but using the church calendar, ie the Julian calendar. That date happens to be January 7 on the Gregorian calendar, which is used for secular purposes.
Orthodox Christmas is usually mentioned in our local news media, given the large number of Ukrainian Orthodox folks in our province.
I think the point @doreen was making was that even practicing Orthodox Christians use the Gregorian calendar for everything other than religious purposes, and would not normally be aware of the date of any given day in the Julian calendar. So it’s entirely plausible to imagine a conversation between two Orthodox Christians, with one of them asking “When is Christmas this year?” and the other replying “January 7”, giving an answer in the Gregorian calendar. Of course Christmas is still December 25 in Julian, but that answer is of no use to somebody who’s reckoning time under the Gregorian calendar for everyday purposes.
And now the time has come to make my favourite joke about this in this thread, namely, that Christmas and Halloween are actually on the same day, because Dec 25 = Oct 31.
Black Widower fan, I take it?
Indeed But I must admit I didn’t catch the reference to a particular Black Widower story, if there is one. I haven’t read all of them, though, only a “best of” anthology.
“The Family Man”.
More I won’t say. 
Yep , and it also that it wouldn’t seem quite as strange for some of the non-Orthodox if the calendars had different names for the months - if , for example, the Julian calendar did not contain a month called “December” and Christmas was celebrated on Sixtilus 25 on the Julian calendar , which corresponds to January 7 on the Gregorian calendar. If the calendars had different names for the months there wouldn’t be any " Do the orthodox say Christmas is January 7 or do they say Christmas is December 25?" because only one calendar would have months named “December” and “January”.
The Julian calendar itself went through a reform and the Armenian Orthodox church did not adopt it, so their Christmas is January 19. This is an Oriental Orthodox church, not Eastern Orthodox (it matters), but most OE churches took the reform.
Apparently the Finnish Orthodox church is the only one to use Gregorian fully for Christmas and Easter.
England being slow to adopt the Gregorian calendar is why you can say that William Shakespeare and Miguel de Cervantes died on two dates in row, but weeks apart.
The October Revolution was in November, as Russia was still using the Julian calendar for everything at that point.
I’m sorry, but there was no reform to the Julian calendar until the Gregorian calendar. Or if there was one, I’d like to see a cite.
January 19 is the Gregorian date of the Epiphany in the Eastern Orthodox religious calendar, and that’s what they would be celebrating on that day. Some people (and perhaps Armenians are among them) do the exchange of gifts on Epiphany because that celebrates the Magi bringing gifts to Jesus.
Ah, that’s right, Epiphany is the celebration date, I misread.
That’s one of the interesting trivia questions:
Q: What month was the October Revolution in?
A: November.
Q: Where are Panama Hats originally made?
A: Ecuador
Q: What was King George VI’s first name?
A: Albert