+ AA6YQ comments below
I was kind of expecting this answer. Still I do not understand, why the most common European way of writing the date is idiosyncratic ...
When I do large numbers of cards, I use BV7 from DF3CB, where I can put the date in any format. But for quick answering/printing a small number of cards, I was hoping to use DXKeeper with an easy to understand date format.
+ Yours is the first request for an additional date format since the DD-MMM-YY options were made available in DXKeeper 8.7.0 - 11 years ago. One request per decade is idiosyncratic.
+ The YYYY-MM-DD format is a worldwide (ISO) standard, and is unambiguous as to meaning.
+ The DD-MMM-YY formats were easy to add because they require less horizontal space than the YYYY-MM-DD format . Adding a DD-MMM-YYYY format would break both the QSL card and QSL label layouts because it contains more characters than the YYYY-MM-DD format. Whichever columns I choose to shrink to compensate would make some set of users unhappy.
+ Because I could spend all of my available time creating new QSL card and QSL label layouts, I have intentionally kept DXKeeper's generated QSL cards and labels utilitarian, pointing users who want more flexibility to DXKeeper's ability to "drive" more flexible QSL card generators like BV7 with an ADIF or tab-delimited file exported from the QSL Queue.