I recently updated the article on the Our Faith page of the Sts. Anargyroi website and the subject was All Saints day, which in the Orthodox world is celebrated the Sunday after Pentecost. You can read it here. These small write-ups I do every so often on the parish site are not meant to be definitive but rather to be informative and to make us think. The Wiki article, which is a very good summary of the various All Saints traditions, goes more in depth into the Leo the Wise story and mentions that the all saints commemoration was originally a commemoration of all martyrs and that Leo, with his dedication of a church for all saints, got the ball rolling on expanding the scope of the day.
While printing out the Orthros service for this Sunday today at church I was pleased as punch to find a remnant of the old (pre-9th century) commemoration; the troparion (theme song, basically) for the feast is actually a commemoration of the martyrs, not all saints, and thus connects it with the original intent of the day. I imagine this hymn predates the All Saints practice and has stuck with us through all of these years. Below is the Fr. Seraphim Dedes translation.
Your Church is arrayed in the holy blood of Your Martyrs who witnessed throughout the world, as though in purple and fine linen. Through them she cries to You, Christ our God, ?Send down to Your people Your tender love, grant peace from above to Your com? monwealth, and to our souls Your great mercy.?