I currently use a different countdown app. I liked the look of Countdowns, and the watch complication is very well done (and even supports the new Infograph watch face), so I downloaded it to try. Unfortunately, when counting down by days (as opposed to days+hours+minutes) there is a weird off-by-one design in the this app from Countdowns. For example, if you have a countdown to your birthday, you'd reasonably expect the count to be "2" when it is two days before your birthday, "1" on the day before your birthday and "0" on your birthday itself. That makes sense and matches how people talk about the concept of "how many days until".
Countdowns is different: "2" in Countdowns is *three* days before your birthday, "1" is two days before your birthday, and "0" is the day before your birthday. On your birthday itself, the counter reads "364" days, using the logic that it's now 364 days until your *next* birthday. I think I understand why Countdowns was written this way: strictly speaking, on the day before your birthday, it's less than 24 hours to go, so it's not one full "day", and so Countdowns shows it as "0" days to go. The problem is that this is not how people think of and speak about this app (or how other countdown apps work). To humans, the rocket launches at zero, not at negative 1.
I love the rest of the features, but this sort of breaks it for me.