No, Sunday is always a feast day.
@SabbathBlessings @Lukaris By the end of the 600s AD, a controversy arose at the Council of Trullo regarding whether it was appropriate to fast on Saturdays, a practice that was observed in Rome but not elsewhere. Canon 55 of the Council states:
“Since we understand that in the city of the Romans, in the holy fast of Lent they fast on the Saturdays, contrary to the ecclesiastical observance which is traditional, it seemed good to the holy synod that also in the Church of the Romans the canon shall immovably stand fast which says: ‘If any cleric shall be found to fast on a Sunday
or Saturday (except on one occasion only) he is to be deposed; and if he is a layman he shall be cut off.’”
In the East, the issue long preceded the Council of Trullo and was based on the
sabbath having been a day for rest and prayer similar, though
distinct, from Sunday. This tradition is seen in the Apostolic Constitutions:
“But assemble yourselves together every day, morning and evening, singing psalms and praying in the Lord’s house: in the morning saying the sixty second Psalm, and in the evening the hundred and fortieth, but principally on
the Sabbath day. And of
the day of our Lord’s resurrection, which is the Lord’s day, meet more diligently, sending praise to God that made the universe by Jesus, and sent him to us, and condescended to let him suffer, and raised Him from the dead. Otherwise, what apology will he make to God who does not assemble on that day to hear the saving word concerning resurrection?”