For others that may struggle with this, your excells/dhtmlxgrid_excell_dhxcalendar.js as supplied sets the date format to european d/m/y
Your documentation refers to M/d/Y as the “default” date format (not european) all over the place, so it took me a while to find this is where I need to change things.
Sorry for misleading information in our documentation.
Actually, it should be updated - we will necessarily add information about the new calendar there.
dhxcalendar has the following default format:
%d/%m/%Y
And it can be changed by setDateFormat method:
grid.setDateFormat(new_format);