An answer: We usually assume DnD worlds work like our unless otherwise stated. So in the absence of specific moon rules, we presume that there’s one moon with about the same cycles.A side note on this whole conversation and just an observation. Why is it that we seem to do we assume that all D&D fantasy worlds have a moon like ours? Or that the moon is on a monthly cycle? This came up in a Ravenloft game - that the moon was full more often, once every 10 days. My immediate question was - is that unusual for Faerun? Does the world have only a single moon which is a bit of an oddity in our solar system, or is it a specific moon?
I don't want to derail, just a thought to ponder when doing world design.
Some settings do make those changes; Dragonlance comes to mind. But as far as I know FR and all the homebrew settings I’m playing in have an earth-like moon.
And frankly, changing the moon is usually more trouble than it’s worth, unless you’re going to tie something core to the setting to the new moon rules. Again, c.f. Dragonlance and the moons affecting magic based on the caster’s alignment (but there’s reasons most settings don’t do stuff like that.)
In short, if the setting premise doesn’t imply werewolves will be important, I would expect the moon there to work like the moon here.