Think about this:
Sleeper: 7 letters.
October 7th: 7 letters in the word October.
It's the 7th day of the month.
Armsday: 7 letters.
[spoiler]2spooky[/spoiler]
Edit: The word letters has 7 letters.
Edit: The number 7 has 7 in it.
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It all make sense now