Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Councils of Ancyra, Gangra, Neocæsarea, Antioch and Laodicea, which Canons were Accepted and Received by the Ecumenical Synods.: Canon VI

Canon VI.

Concerning those who have yielded merely upon threat of penalties and of the confiscation of their goods, or of banishment, and have sacrificed, and who till this present time have not repented nor been converted, but who now, at the time of this synod, have approached with a purpose of conversion, it is decreed that they be received as hearers till the Great Day, and that after the Great Day they be prostrators for three years, and for two years more communicate without oblation, and then come to full communion, so as to complete the period of six full years.  And if any have been admitted to penance before this synod, let the beginning of the six years be reckoned to them from that time.  Nevertheless, if there should be any danger or prospect of death whether from disease or any other cause, let them be received, but under limitation.

Notes.

Ancient Epitome of Canon VI.

A man who yielded to threats alone, and has sacrificed, and then repented let him for five years be a prostrator.

Zonaras.

But should any of those debarred from communion as penitents be seized with illness or in any other way be brought nigh to p. 66 death, they may be received to communion; but in accordance with this law or distinction, that if they escape death and recover their health, they shall be altogether deprived again of communion until they have finished their six years penance.

Hammond.

“The Great Day,” that is, Easter Day.  The great reverence which the Primitive Church from the earliest ages felt for the holy festival of Easter is manifested by the application of the epithet Great, to everything connected with it.  The preceding Friday, i.e., Good Friday, was called the Great Preparation, the Saturday, the Great Sabbath, and the whole week, the Great Week.