That makes no historical sense whatsoever.
Especially when Halloween only begins to be celebrated, After the Pope first establishes the All Saint's Day celebration, to which All Hallow's "Eve" would eventually become the "Eve" to.
Even then, you're still waiting for after the four century period where said holy day celebrations were celebrated in the Spring...
Before popularity, coupled with end of winter food scarcity, made the Pope's move the now weeklong event to after the harvest was brought in. The first week of November.
Then it's a couple centuries for pre All Hallow Saint's day, to become Essentially a celebration in itself. Much like Christmas Eve or New Year's Eve, today.