Each day has (exactly) 24 hours, each with (exactly ) 60 minutes. Therefore, each day has 24 X 60 equals (exactly) 1440 minutes. 21,573,834/1440 = 14,981.829 days, to the justified number of...
That depends when you think the day begins and ends. IF you think of the day as including the night (24 hours) then they don't get longer or shorter at all. The only appear to because it gets darker...