You sure can! We get asked this all the time.
The simplest way is to log in to your account and head to your Settings. From there you can change your monthly billing day to whatever tickles your fancy. And we always ship your box off the day after billing so you'll know just when to expect your box!
It's worth noting however that you can't make this change if the current box is already pending (ie we've made some great wine recommendations). Any change you make at this time will only be reflected in your next box.
You can change this day whenever you like and as many times as you like, we've got no restrictions on that. We just want what works for you :)