On 13 May 609 or 610, Pope Boniface IV consecrated the Pantheon at Rome to the Blessed Virgin and all the martyrs, ordering an anniversary; the feast of the "dedication Sanctae Mariae ad Martyres" has been celebrated at Rome ever since. It is suggested 13 May was chosen—by the Pope and earlier by Christians in Edessa—because it was the date of the Roman pagan festival of Lemuria, in which the malevolent and restless spirits of the dead were propitiated. Some liturgiologists base the idea that Lemuria was the origin of All Saints on their identical dates and their similar theme of "all the dead".