With other numbers, non-date numbers, we put the numbers representing the most quantity to the left, and numbers representing the last quantity to the right, eg 1 hundred, ten and 1 would be 111, where the number representing 100 qty comes first from the left, and each position moving to the right, represents a smaller and smaller amount.

Since years are longer than months, which are longer than days, the YYYY-MM-DD format actually follows the same convention that we commonly use for all other numbering systems, big on the left, small on the right.

So why would the date be the exception?