From a Facebook post from the Rev. Tim Brown:

Today the church celebrates All Saints Day, the day in which the formal saints of the church (those canonized) are recognized and remembered as examples of the faith.

This celebration is very old, perhaps dating back to the 4th Century, though it is clear that earlier commemorations of this feast day were held in the spring, sometime between Easter and Pentecost. It was originally intended to celebrate not just any saints, but the martyrs of the faith.

The focus and the date of the day shifted sometime just before or in the early 7th Century. In the British Isles it had already been honored on November 1st, probably in response to the pagan autumn festivals that culminated at the end of October (which many of you participated in last night with ghosts and goblins at your door!). The date stuck for the whole church within the century, and came to have a deeper connection not only with the seasonal cycle on display in the northern hemisphere, but also with pre-Christian sensibilities. One example is this Celtic idea that the arrival of mists and frosts around this time were examples of ghostly/faery visitors, so it made sense to have a day remembering them when they started to make their presence known again.

In the 7th Century the date came to commemorate non-martyrs as well, probably in response to the fact that Christianity became dominant and was less-oppressed…resulting in fewer martyrs of the faith. The faithful who died both naturally and by martyrdom were recognized on this date every year, especially if they had died in that calendar year.

Today Orthodox, Roman Catholic, and Anglican branches of liturgical Christianity still keep this day to honor those canonized saints of the church, reserving the non-canonized dead to be remembered tomorrow on All Souls Day (more on that tomorrow). Lutherans, with our penchant for comingling the idea of “sinner and saint,” usually don’t make such a distinction, and just honor all those who have died in the faith, regardless of status, on this day.

Whatever your proclivity, today is a powerful day when honored with intention, even for those of you who don’t find yourself in any faith tradition. Honoring our ancestors, learning from their stories, embracing their goodness and foibles, is an important part of the human experience in my estimation. We all are, after all, an unwilling product of those who came before us, but we continually have a choice in deciding what we’re going to carry with us from those past ancestors, and what we’re not going to let continue into the next generation.

All Saints Day is a reminder for me, and should be for the whole church, that those who came before still speak into our present, and that the Divine who seems in love with continual creation also seems in love with some measure of continual, constant, though hidden and obscure (like through a mirror darkly?) preservation.

-historical bits from Pfatteicher’s _New Book of Festivals & Commemorations_

-opinions and Celtic reflections mine