Very frustrating not to be able to apply per-column date formats exporting to Excel
When exporting to Excel, it is possible to add multiple number formats and then use `set_column` to apply any desired numeric format to any column. Attempting to do the same for date or date-time columns has no effect however.

It is possible to set a format for all date columns or all date-time columns using the `date_format` and `datetime_format` arguments to `ExcelWriter()`, but that applies a single format to all dates and a single format to all date-time values.

In my particular case, I have a column that is intended to represent a whole month, and I want to format it as such in the exported data, and I have other date columns that represent specific dates. There is apparently no way to accomplish that. Why?

Why not simply allow applying date formats to columns just as one can apply numeric formats to columns? 