Today I used the Date Field for the first time in ACF 5 and note that the calendar dropdown is not perfect. In ACF 4.x the display is much better
ACF 5
ACF 4.x
In ACF 5 the design looks very flat and is difficult to read. I tried this on a new WP 4.0 installation to be save this causes not on any other plugin.
It would be great if the ACF 5 Date Field get the same look as in V 4.x