it's far more sensible to use the mathematical convention of largest units to the left to smallest on the right.
Says who? When I went to school my maths teacher taught me [along with everyone else] to start counting from the lowest number, that being 1, then upwards.... being there is an infinite number of numbers, and you cannot start at an end which in essence does not exist
So, using that as the most logical mathematical convention, the smaller number would obviously come first... which for the purpose of this deba...er, argument, it the day, followed by the month, which is next smallest and the next logical progression, then the year, which defines which period in the decade/century those days and months belong.
Like anything else in life... you start at the bottom and work up. For example, and as an architect you'd know this, you don't first put up the roof and shove the walls in under later.
So again, says who?
[yeah, you guessed it, I've nothing better to do than be a right royal pain in the....]