Today's Halloween customs are also thought to have been influenced by Christian dogma and practices derived from it. Halloween is the evening before the Christian holy days of All Hallows' Day (also known as All Saints' or Hallowmas) on 1 November and All Souls' Day on 2 November, thus giving the holiday on 31 October the full name of All Hallows' Eve (meaning the evening before All Hallows' Day).[61] Since the time of the early Church,[62] major feasts in the Christian Church (such as Christmas, Easter and Pentecost) had vigils which began the night before, as did the feast of All Hallows'.[63] These three days are collectively referred to as Allhallowtide and are a time for honoring the saints and praying for the recently departed souls who have yet to reach Heaven. All Saints was introduced in the year 609, but was originally celebrated on 13 May,[64] the same date as Lemuria, an ancient Roman festival of the dead. In 835, it was officially switched to 1 November, the same date as Samhain, at the behest of Pope Gregory IV.[64] Some suggest this was due to Celtic influence, while others suggest it was a Germanic idea,[64] although it is claimed that both Germanic and Celtic-speaking peoples commemorated the dead at the beginning of winter.[65] It may have been seen as the most fitting time to do so, as it was when the plants themselves were 'dying'.[65][64] It is also suggested that the change was made on the "practical grounds that Rome in summer could not accommodate the great number of pilgrims who flocked to it", and perhaps because of public health considerations regarding Roman Fever – a disease that claimed a number of lives during the sultry summers of the region.[66]