Leap Year matters. If you paid attention in Earth Science class you know that the orbit of the Earth around the sun isn’t an exact amount of rotations of the Earth ie. Days. Our calenders have to be adjusted to match up. If we didn’t do this. the star constellations wouldn’t match our calenders, and our seasons would start to drift out of the expected months and equinox and solstice would end up all over in our calenders. We can’t have that! Leap year IS observed around the world and of course every one agrees on it because we know about the Earth’s rotation around the sun. As for the changing of the clocks on a seasonal basis, often known as ‘Daylight Savings’ that does differ from region to region and it is based on the daylight hours and making the most of them. I live at 63N latitude, and our daylight savings is observed at a different time than most of the US.