over 1 year ago - Shurenai - Direct link
When you change any setting that affects when a horde night is, it recalculates from the current day. So no horde night is technically 'skipped', but it won't occur on day 14/15.

So being on Day 13, if you set it to 3 days with the same +/-1, your next horde should be on day 15-17.

That said, Even if it was skipped, it wouldn't matter much since horde night difficulty is tied to your gamestage/progress, rather than being based on the number of horde nights that had passed.