how to disable today date on datepicker that follow the time zone.

Hi everythings,

I have a question regarding on disabling today date on datepicker, i got this code from internet and it seem like working , but then i realised its starting disable today date from 08:00 am onward and not disable from 12:00 am, seems like its has problem with time zone, i guess.

$('.datepicker').datepicker({
format: 'dd-mm-yyyy', 
startDate: '+1d',
endDate: '+5m',                              
beforeShowDay: renderCalendarCallback               
});

Does anyone can explain me why this thing happen? TQ in advance.