Between 1024 and 1033 the monks at Cluny began commemorating the Dead Souls on the day after All Saints
In 1049 a monk, Jotsaldus, began to write a life of Odilo, abbot of Cluny (962 – 1048). In this vita, he recounted the story behind the institution of All Souls:
“One day he [Odilo] told me, a monk from Rouergue was on his way back from Jerusalem. While on the high seas between Thessalonika and Sicily, he encountered rough winds. These drove his ship onto a rocky islet inhabited by a hermit, a servant of God. When our man saw the seas calm, he chatted about one thing and another with this hermit. The man of God asked him what nationality he was, and he answered that he was from Aquitaine. The man of God then asked if he knew a monastery, which bears the name of Cluny and the abbot of this place, Odilo. [The Monk) answered: I know him, indeed I know him well, but I would like to know why you are asking me this question. And the other [the hermit] replied: I am going to tell you, and I beg you to remember what you are about to hear. Not far from here there are places where by the manifest will of God, a blazing fire spits with the utmost violence. For a fixed length of time the souls of sinners are purged there in various torments and constantly: each day the devils inflict new pain and make the suffering more and more intolerable.
I have often heard the lamentations of these [devils], who complain violently, since God’s mercy allows these condemned souls to be delivered from their pains by the prayers of monks and by alms given to the poor in holy places Their complaints are above all addressed to the community of Cluny and its abbot. By God, I beg of you, therefore, if you have the good fortune to return to your home and family, to make known to this community what you have heard from my mouth, and to exhort the monks to multiply their prayers, vigils and alms for the repose of souls enduring punishment, in order that there might be more joy in Heaven and the devil may be vanquished and thwarted. Upon returning to his country, our man faithfully conveyed this message to the Holy Father abbot and the brothers [of Cluny]. When they heard him, the hearts of the brothers ran over with joy and they gave thanks to God in prayer after prayer while heaping alms upon alms and working tirelessly that the dead might rest in peace. The holy abbot afterwards proposed to all the monasteries that the memory of all the faithful should be celebrated everywhere on the day after All Saints’ – the 1st of November – in order to secure the repose of the souls; and further that masses with psalms and alms should be celebrated in public and in private, and that alms be distributed unstintingly to all the poor. Thus hard blows would be struck at the diabolical enemy and suffering Christians might cherish the hope of divine mercy”. (PL 142.897 – 940, De vitae et virtutibus S. Odilonis abbatis, liber secundus, Cap. XIII – de quadam vision cujusdam eremitae).
A few years later, Peter Damianus rewrote this story when he was working to have Odilo sanctified. From this account, the vignette was later included and expanded upon in the Golden Legend, by Jacobus da Voraigne (Jacopo da Varazze) on his chapter on The Feasts of all Saints and Souls. According to him, a series of miracles demonstrated the liberation of souls who might be bought by the assiduous intervention of the living though prayers and alms-giving. According to Jacques le Goff, the difference in these two accounts marked the difference between the germ of the purgatory and its full-blown existence in a late medieval context 
In a recent article, the German Scholar Jürgen Bärsch has analysed not only this text but also the actual declaration concerning the institution of All Souls as it is presented in “Statutum odilonis” (as preserved in Cod. Lat. 6808 in the Vatican)
According to his perusal of this text, the intention of the leaders of Cluny was very clearly to weave a community consisting of not only the saints and the monks from Cluny – living as well as deceased – but to create an all-inclusive community inhabited by all Christian souls. To achieve this, the liturgy for the “Commemoratio Omnium fidelium defunctorum” was entwined seamlessly with the liturgy for All Saints. Both were to be understood together and as a “double feast”. Central to this entwining was the chiming of the bells to be heard after vesper on All Saints both on earth as well as in heaven leading directly to a Missa pro defunctis – Mass for the Dead. Next day was to be filled with a series of private masses. Through this liturgical construct, Cluny created a universal ecclesiastical – communitarian – vision bridging both time and place. It was only later the different parts of the celebrations were metered out as redemption for (specific) souls in the purgatory; a practice which later resulted in the Lutheran condemnation of All Souls, believing that the institution of this feast around 1000 AD was merely a way of embedding the popular (heathen) festival of the equinox in the church calendar of the autumn and at the same time creating a market to sell “masses”. Thus – while both All Saints and Souls continued to be celebrated in the Catholic Church, the two feasts collapsed into one amongst the Lutherans.
Curiously enough this has meant that while the celebration of all Souls and Saints in Catholic contexts has kept some of its character as a popular festival marked by souling and the distribution of sweet cakes – Soul Cakes (in German: Seelenkuche or Seelenspitzen – the re-invention of the Lutheran tradition in Scandinavia in the 20th century has been accompanied by a series of much more church-oriented traditions like candles on the graves  and extensive chiming of the church bells.
The modern tradition of Halloween – currently being marketed vigorously by shopping malls – may have roots back in the guising and mumming amongst the Irish and the Scots in the 15th and 16th century. Halloween, though, is essentially an American custom, which evolved in the 20th century, and which has only unspecific affinity to series of popular customs located in the weeks between Michaelmas and Martinmas. The idea, though, that the custom has Celtic roots seems even more farfetched. Probably this misconception is rooted in the beliefs of Protestant or Anglican theologians voicing their disrespect for “our invention” as it came to be played out in the later Middle Ages. (But the full story of the folklore and the different European folk-customs still awaits a proper analysis.)
 The Birth of Purgatory
By Jacques le Goff
The University of Chicago Press 198, p. p. 125 – 127
 Ljusen på gravene og andre lysvaner. Nye traditioner i 1900-tallet. ByMats Rehnberg.
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Heaven Can Wait: Purgatory in Catholic Devotional and Popular Culture
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Miscellanea secundum usum ordinis Cluniacensis: Consecration of the Abbey of Cluny by Pope Urban II in 1095. Mauscript 17716, f.91r Paris, Bibliotheque Nationale de France.