Vertical Date Format for Table

I have been playing around with using SVG to do that (rotating the text).  It is possible but ultimately not worth the hassle as you would also need to disable auto column sizing and then have to modify the column width for new dates manually.

If this is important to you please consider voting for an existing idea or raising a new one at https://ideas.fabric.microsoft.com/?forum=2d80fd4a-16cb-4189-896b-e0dac5e08b41