Legacy is a big factor. I imagine it may endure in part because you often care most about month-then-day. Year is less important when one cares about the most r

Legacy is a big factor. I imagine it may endure in part because you often care most about month-then-day. Year is less important when one cares about the most recent data. IMO YYYY-MM-DD and MM-DD are best, and I try to use them everywhere I can.