Canon LXXXIX.

The faithful spending the days of the Salutatory Passion in fasting, praying and compunction of heart, ought to fast until the midnight of the Great Sabbath:  since the divine Evangelists, Matthew and Luke, have shewn us how late at night it was [that the resurrection took place], the one by using the words ὀΨὲ σαββάτων, and the other by the words ὄρθρου βαθέος.

Ancient Epitome of Canon LXXXIX.

On the Great Sabbath the fast must be continued until midnight.