beforeShowDateが機能しなかったので、先に進んで独自のソリューションを開発しました。
$('#embeded_calendar').datepicker({
minDate: date,
localToday:datePlusOne,
changeDate: true,
changeMonth: true,
changeYear: true,
yearRange: "-120:+1",
onSelect: function(selectedDateFormatted){
var selectedDate = $("#embeded_calendar").datepicker('getDate');
deactivateDates(selectedDate);
}
});
var excludedDates = [ "10-20-2017","10-21-2016", "11-21-2016"];
deactivateDates(new Date());
function deactivateDates(selectedDate){
setTimeout(function(){
var thisMonthExcludedDates = thisMonthDates(selectedDate);
thisMonthExcludedDates = getDaysfromDate(thisMonthExcludedDates);
var excludedTDs = page.find('td[data-handler="selectDay"]').filter(function(){
return $.inArray( $(this).text(), thisMonthExcludedDates) >= 0
});
excludedTDs.unbind('click').addClass('ui-datepicker-unselectable');
}, 10);
}
function thisMonthDates(date){
return $.grep( excludedDates, function( n){
var dateParts = n.split("-");
return dateParts[0] == date.getMonth() + 1 && dateParts[2] == date.getYear() + 1900;
});
}
function getDaysfromDate(datesArray){
return $.map( datesArray, function( n){
return n.split("-")[1];
});
}