Could you please quote the canon on this? I think you will find the practice already well established.
I find it telling that the church at Rome would want to discontinue (change) the celebration that John, the last living Apostle, brought to these churches in Asia Minor.
The Church at Rome followed the practice of Sts. Peter Paul (as did that of Antioch). The Church at Alexandria followed the same practice thanks to St. Mark. The practice allegedly being tied back to St. John was held by one small sector of Judaizers. It is not at all certain that this wasn't a more recent innovation in any case, which seems more likely since it was only this small area that adhered to this practice.
From the Letter of the Emperor to all those not present at the Council.
(Found in Eusebius, Vita Const., Lib. iii., 18-20.)
When the question relative to the sacred festival of Easter arose, it was
universally thought that it would be convenient that all should keep the
feast on one day; for what could be more beautiful and more desirable,
than to see this festival, through which we receive the hope of
immortality, celebrated by all with one accord, and in the same
manner? It was declared to be particularly unworthy for this, the
holiest of all festivals, to follow the custom [the calculation] of the
Jews, who had soiled their hands with the most fearful of crimes, and
whose minds were blinded. In rejecting their custom,(1) we may
transmit to our descendants the legitimate mode of celebrating Easter,
which we have observed from the time of the Saviour's Passion to the
present day[according to the day of the week]. We ought not,
therefore, to have anything in common with the Jews, for the Saviour
has shown us another way; our worship follows a more legitimate and
more convenient course(the order of the days of the week); and
consequently, in unanimously adopting this mode, we desire, dearest
brethren, to separate ourselves from the detestable company of the
Jews, for it is truly shameful for us to hear them boast that without
their direction we could not keep this feast. How can they be in the
right, they who, after the death of the Saviour, have no longer been led
by reason but by wild violence, as their delusion may urge them? They
do not possess the truth in this Easter question; for, in their blindness
and repugnance to all improvements, they frequently celebrate two
passovers in the same year. We could not imitate those who are openly
in error. How, then, could we follow these Jews, who are most
certainly blinded by error? for to celebrate the passover twice in one
year is totally inadmissible. But even if this were not so, it would still
be your duty not to tarnish your soul by communications with such
wicked people[the Jews]. Besides, consider well, that in such an
important matter, and on a subject of such great solemnity, there ought
not to be any division. Our Saviour has left us only one festal day of
our redemption, that is to say, of his holy passion, and he desired[to
establish] only one Catholic Church. Think, then, how unseemly it is,
that on the same day some should be fasting whilst others are seated
at a banquet; and that after Easter, some should be rejoicing at feasts,
whilst others are still observing a strict fast. For this reason, a Divine
Providence wills that this custom should be rectified and regulated in a
uniform way; and everyone, I hope, will agree upon this point. As, on
the one hand, it is our duty not to have anything in common with the
murderers of our Lord; and as, on the other, the custom now followed
by the Churches of the West, of the South, and of
the North, and by some of those of the East, is the most acceptable, it
has appeared good to all; and I have been guarantee for your consent,
that you would accept it with joy, as it is followed at Rome, in Africa,
in all Italy, Egypt, Spain, Gaul, Britain, Libya, in all Achaia, and in the
dioceses of Asia, of Pontus, and Cilicia. You should consider not only
that the number of churches in these provinces make a majority, but
also that it is right to demand what our reason approves, and that we
should have nothing in common with the Jews. To sum up in few
words: By the unanimous judgment of all, it has been decided that the
most holy festival of Easter should be everywhere celebrated on one
and the same day, and it is not seemly that in so holy a thing there
should be any division. As this is the state of the case, accept joyfully
the divine favour, and this truly divine command; for all which takes
place in assemblies of the bishops ought to be regarded as proceeding
from the will of God. Make known to your brethren what has been
decreed, keep this most holy day according to the prescribed mode; we
can thus celebrate this holy Easter day at the same time, if it is granted
me, as I desire, to unite myself with you; we can rejoice together,
seeing that the divine power has made use of our instrumentality for
destroying the evil designs of the devil, and thus causing faith, peace,
and unity to flourish amongst us. May God graciously protect you, my
beloved brethren.
from DOCUMENTS FROM THE FIRST COUNCIL OF NICEA [THE FIRST ECUMENICAL COUNCIL] A.D. 325
This is the Decree from the first Pontiff of the Roman church to all.
b'shem Y'shua