Strictly speaking, such a button is not needed. Once the range has been narrowed down to a single date, it could automatically proceed to the next step. However, the lack of such a button does force the user to take the maximum number of steps every time.
I am guessing the range is non-inclusive of the edge values, so there’s really no way to confirm the correctness once you land on the correct date and pressing either button automatically labels it incorrect and excludes it from the range. So I would argue that it is necessary
Also there’s no way to go back when you make a mistake
Strictly speaking, such a button is not needed. Once the range has been narrowed down to a single date, it could automatically proceed to the next step. However, the lack of such a button does force the user to take the maximum number of steps every time.
I am guessing the range is non-inclusive of the edge values, so there’s really no way to confirm the correctness once you land on the correct date and pressing either button automatically labels it incorrect and excludes it from the range. So I would argue that it is necessary
Also there’s no way to go back when you make a mistake