When I was a kid, I read somewhere that the reason a year is such a screwy number is explained biblically. In the Bible there are passages, but I can only remember one, where an Israeli general prayed to God that night wouldn’t occur during a batlle, because then the enemy would be able to flee. God obliged and kept the sun from setting until the battle was done. TDon’t know if that’s why we have an extra day, but it works for me.
Some Creationists argue that perhaps, as a consequence of the flood catasphrophe, or maybe when the “world was divided” at the time of the Tower of Babel, the Earth could have lost some of its mass. That would have affected the rate of spin and the velocity of the Earth and changed the length of days and years.
Not something you can prove through Scripture, but it would be an interesting correlary to how man became flawed, with shorter and shorter lifespans after the fall, if the Earth itself became flawed too.