This PR intends to close [ENH]: Support using datetimes as positions argument to violin(...) #30417

It should be possible to set the position of a violin plot to be a datetime. Currently, an attempt to do this results in this error message: TypeError: unsupported operand type(s) for +: 'float' and 'datetime.datetime'

The error stems from trying to perform operations between float and datetime if datetime was provided as position arguments.

The proposed solution improves the error message to be:

"If positions are datetime/date values, pass widths as datetime.timedelta (e.g., datetime.timedelta(days=10)) or numpy.timedelta64.

unit tests are in tests\test_violinplot_datetime.py

I had opened another PR 30508, but messed up the commits while making changes. I am making this one after reading the suggestion here: #30508 (comment) by @rcomer . This change updates the error message instead of converting the position and width