In the year 609 or 610 Pope Boniface IV established a date for All Saints’ Day on May 13th. And later, in the early 700s AD, Pope Gregory III changed the date to November 1st. Decrees like this took some time to propagate from Rome to the more remote areas where the Church was found. But the change in date had nothing to do with any pagan practices. Pope Gregory IV extended the celebration on this day to the entire Western Church in the early 800s. And again, the change took time as it spread from Rome.
The point is this: a common day for commemorating the Saints has been around throughout the Christian Church from very early times. And the fact that it falls on November 1st today has nothing to do with paganism.