Agreed, this needs a title to be meaningful.

The writing on the time axis is far too small, and uses the times “12am” and “12pm”, neither of which exist.

Edit to add: Beautiful data is not ambiguous. Midnight and noon are the unambiguous terms you are looking for. 12 noon is the meridiem and can be neither ante nor post itself. 12 midnight is both 12 hours post meridiem and 12 hours ante merdiem.

Of course, all that nonsense could be avoid if the 24-hour clock had been used for the scale instead.