From Day One:

Shared Journals are a private space for your closest friends and family to shared life updates and memories. Shared Journals introduce a new dimension to journaling, offering a unique way to share your personal stories and experiences with up to 30 selected individuals, while keeping your individual entries private and secure.

I’ve tried to track most of the milestones in the lives of my kids in Day One, and knowing I can now share that with my partner is pretty awesome. I’ve been using tags to group these posts but now I can break them into their own journal that I can share and collaborate on. Day One is one of the best apps out there due to their constant iteration on an already outstanding product. I’m really glad to see they continue to thrive as part of Automattic, as I was a bit concerned when that acquisition went down a few years back.