The Nicene Creed is a declaration of faith stated by the church fathers on the Council of Nicaea (325 AD). This is the first creed solving crucial doctrinal issues and church disunity.
The content of the creed is following:
Πιστεύομεν εἰς ἕνα Θεὸν Πατέρα παντοκράτορα, πάντων ὁρατῶν τε και ἀοράτων ποιητήν.
Πιστεύομεν εἰς ἕνα Κύριον Ἰησοῦν Χριστόν, τὸν υἱὸν τοῦ Θεοῦ, γεννηθέντα ἐκ τοῦ Πατρὸς μονογενῆ, τοὐτέστιν ἐκ τῆς οὐσίας τοῦ Πατρός, Θεὸν ἐκ Θεοῦ ἀληθινοῦ, γεννηθέντα, οὐ ποιηθέντα, ὁμοούσιον τῷ Πατρί
δι' οὗ τὰ πάντα ἐγένετο, τά τε ἐν τῷ οὐρανῷ καὶ τὰ ἐπὶ τῆς γῆς
παθόντα, καὶ ἀναστάντα τῇ τρίτῃ ἡμέρᾳ, καὶ ἀνελθόντα εἰς τοὺς οὐρανούς, καὶ ἐρχόμενον κρῖναι ζῶντας καὶ νεκρούς.
Καὶ εἰς τὸ Ἅγιον Πνεῦμα.
Τοὺς δὲ λέγοντας, ὅτι ἦν ποτε ὅτε οὐκ ἦν, καὶ πρὶν γεννηθῆναι οὐκ ἦν, καὶ ὅτι ἐξ οὐκ ὄντων ἐγένετο, ἢ ἐξ ἑτέρας ὑποστάσεως ἢ οὐσίας φάσκοντας εἶναι, ἢ κτιστόν, τρεπτὸν ἢ ἀλλοιωτὸν τὸν Υἱὸν τοῦ Θεοῦ, τούτους ἀναθεματίζει ἡ καθολικὴ καὶ ἀποστολικὴ Ἐκκλησία.
We believe in one God, the Father Almighty, Maker of all things visible and invisible.
And in one Lord Jesus Christ, the Son of God, begotten of the Father the only-begotten; that is, of the essence of the Father, God of God, Light of Light, very God of very God, begotten, not made, being of one substance with the Father
By whom all things were made both in heaven and on earth
Who for us men, and for our salvation, came down and was incarnate and was made man;
He suffered, and the third day he rose again, ascended into heaven;
From thence he shall come to judge the quick and the dead.
And in the Holy Ghost.
But those who say: 'There was a time when he was not;' and 'He was not before he was made;' and 'He was made out of nothing,' or 'He is of another substance' or 'essence,' or 'The Son of God is created,' or 'changeable,' or 'alterable'— they are condemned by the holy catholic and apostolic Church.
The purpose of the creed is to define orthodox Christianity against sentiments of heretical groups (such as Arians, Gnostics, etc.).
Easter Celebration Date
One of the key issues that was addressed at the council was the proper way to calculate the date of Easter. Before the council, the celebration of Easter was observed on different dates by different Christian communities. Some Christians, known as Quartodecimans, celebrated Easter on the 14th day of the Jewish month of Nisan, regardless of the day of the week. Others celebrated on the Sunday following the first full moon after the vernal equinox, which is the beginning of spring. This discrepancy in the date of Easter created confusion and disunity among Christians.
The First Council of Nicaea sought to bring uniformity to the celebration of Easter. The bishops agreed that Easter should be celebrated on the first Sunday following the first full moon after the vernal equinox. This decision was intended to separate the Christian celebration from the Jewish Passover and to ensure that all Christian communities observed the holiday on the same day.
The council also established the Alexandrian Church as the authority responsible for calculating the date of Easter, since they had access to advanced astronomical knowledge at the time. Over the years, various methods have been developed to calculate the date, and the current method in use by most Western Christian churches is the Gregorian calendar-based computation.