I've been 30+ years in IT and for me down arrow always mean: decrease (volume, value), subtract, move backward etc. Pressing the down button on the left or right side of any mobile device means volume down. Period.
For Microsoft (in Windows 11) it means increase (month):
This is as nonsensical, stupid and not obvious as it can be. I find myself always changing the calendar month in the opposite direction. My mind says "press down arrow to go backward" while Microsoft designers said "press down arrow to go forward".
What am I missing?