Which Orthodox churches are on the New Calendar, and which are on the Old Calendar? I'm trying to determine whether or not a majority of Orthodox are on the Old or on the New Calendar.  I don't need numbers for this question, but I do need names. 

Who are on the Old, and who are on the New?

This wiki claims that the "churches of Constantinople, Alexandria, Antioch, Greece, Cyprus, Romania, Poland, Bulgaria, and most of the Orthodox Church in America." are on the New Calendar.

Ok, good start. Is that comprehensive?

This wiki page states that "Those Orthodox Churches which remain in full communion with the New Calendarists and yet continue to use the Julian calendar, include the Orthodox Church of Jerusalem, the Russian Orthodox Church, the Serbian Orthodox Church, and the Georgian Orthodox Church. (The Julian calendar is also used by the Russian Orthodox Church Outside of Russia which has reunited with the Russian Orthodox Church.) Mount Athos subordinate to the Patriarchate of Constantinople also follows the Julian Calendar."

Ok, not comprehensive. If the Wiki page is accurate, the Old Calendar churches include Jerusalem, Moscow, Serbian, Georgian, ROCOR, Mount Athos, and all other Old Calendar churches who are not in communion with Constantinople.

I don't think it is comprehensive, however, as there is a Palestinian Orthodox church in my area that is in communion with Constantinople (and under their authority) who is on the Old Calendar.

I'm also unsure of how to obtain a list of Orthodox churches which are not in communion with Constantinople and who are on the Old Calendar.
This issue gets super confusing, and you probably won't get &quot;comprehensive.&quot; The one thing you got going for you is that if you ask any Orthodox Christian which calendar they follow, they'll have an answer for you lickedy-split, due to how divisive this issue has been historically and still continues to be.
Okay. There is actually two distinct &quot;new calendars&quot; and only one &quot;old calendar.&quot; The &quot;old&quot; is the Julian calendar, it is a reformed and corrected Roman calendar introduced by Julius Caesar in 46 B.C. A good but slightly technical overview is here. The &quot;new&quot; is actually the Revised Julian or the Gregorian. As you may know the Gregorian is the one we are all familiar with. The Revised Julian is essentially the Gregorian but ties the date of Pascha to the Julian calendar. Few Orthodox churches use the Gregorian exclusively.
From Orthodoxwiki:

-The Julian Calendar churches are: Jerusalem, Russia, Serbia, Georgia, Poland, Sinai, Ukraine, and Japan.
-The Revised Julian Calendar churches are: Constantinople, Alexandria, Antioch, Romania, Bulgaria, Cyprus, Greece, Albania, Czech Lands and Slovakia, Estonia and the OCA.
-The Gregorian Calendar church is: Finland.
A number of the above churches also have some parishes and dioceses which are on a different calendar than their respective primates, most especially the Ecumenical Patriarchate of Constantinople in the diaspora, which has many Julian Calendar parishes.

Each Orthodox Church or Jurisdiction has chosen which calendar they will follow. What makes it difficult, and why &quot;comprehensive&quot; will escape us is because so many parishes and dioceses have made calendar decisions that are not always in line with their &quot;mother-Church.&quot;
For information on each of the churches listed above, I would suggest visiting Orthodoxwiki.org's list of autocephalous and autonomous churches. Most of the listed Churches' pages include a sidebar that will tell you which calendar they follow. For those that do not, there may be more information in the article. Hope that helps.