If we really want to get technical about events such as Pascha on the calendar, perhaps we should examine what EO St. Polycarp celebrated, which is the passover feast - not the Sunday after. That is the true "old calendar". You do realize that the Quartodecimans were condemned as heretics? Or, in your fascination with those alternate "successions" in groups the Church has also condemned for heresy, does that fact really matter to you?
As scholar Sacha Stern has pointed out, applying the word "quartodeciman" to the late 2nd-century controversy over the Roman and Asian practices is anachronistic. In the account in History
5.23ff, Eusebius never uses the word "quartodeciman"--at least not in my English translation--nor do any of the authors he quotes. The word cannot confidently be held to have existed before the later 4th century. (A work attributed to a 3rd century author, Hippolytus, uses "quartodeciman" in the caption to a chapter on the practice, but not in the text of the chapter itself. A caption may be the work of a later editor.)
Note also that the Asian practice focused on the 14th of Nisan, not on the day of the Passover Seder, which is the 15th. Eusebius calls the Asians' fast-breaking day "the fourteenth day of the lunar month...the day on which the Jews had been commanded to sacrifice the lamb" -- the day the lamb was slain, not the day on which it was eaten. Polycrates, in the letter quoted by Eusebius, call it "the day the people put away the leaven." The Mishnah
, a source roughly contemporary with Polycrates, indicates that the day of putting away the leaven is the 13th/14th of the lunar month, not the 14th/15th.
On the eve of the fourteenth day of Nisan men search for leaven by candlelight....Rabbi Meir said, "men may eat of it [leaven] until the fifth hour, and burn it at the beginning of the sixth....Rabban Gamaliel said, "men may eat ordinary food till the fourth hour, heave-offering until the fifth hour, but they burned the leaven at the sixth hour."
This is why I suspect, notwithstanding the views of many scholars (for a recent example, Bradshaw, though he relies entirely on secondary sources for his argument), that the Asian practice was to break the fast at the sunset that ended the 13th and began the 14th, or perhaps during the hours of daylight on the 14th, and not, as the scholars hold, during the nighttime hours that began the 15th. But even if my hunch be wrong, it looks to me as though the Sunday custom is just as ancient as the Asian custom. Sunday was a Christian holiday from very early. The Christian Sunday assembly is attested well before any annual Christian festivals are. (At least one scholar, Clemens Leonhard, tries to explain away the New Testament evidence for the Christian Lord's day, but I find his argument unconvincing). It would have been just as easy for the earliest Christians to mark the annual Sunday of Unleavened Bread for special esteem as it would have been for them to mark out the 14th (or 15th) of Nisan for an annual festival.
So the late-2nd century Asian practice was certainly old by the time it became controversial, but I can't find any proof that it was older than the Sunday practice.