I take certain medications that can only be refilled every 28 days. You probably know the ones I’m talking about, am I right? Anyway, I always used to calculate the refill dates in my head, it’s not difficult, and honestly it’s probably better for my cognitive function to do it that way. But I’ve calculated it wrong a time or two - mildly embarrassing to have to be told I came back too soon for my refill. Never happens any more with this Date and Time app. I can spin out 28 days later (coincidentally the title of a fantastic horror flick!), and punch the result straight into my calendar as a reminder. Not only very accurate and very easy, but kinda fun. (It’s great for calculating, say, the next 3 refill dates out, vs doing that in my head.) What can I say? Not an absolute *must-have* like, say, text or maps, but I think I have a couple dozen apps or so on my phone, and only *really* make use of maybe 1 out of 10. And this is one of those. You’ll find your own uses for it, and end up really using it (and liking it), so go on, give this one a go!