Assuming the following...
On May 25th at 1:59 PM, you want to have all dates available, from May 26th
On May 25th at 2:00 PM, you want to have all dates available, from May 27th
If this isn't right, then adjust the hourly increment
In your script, just before the datepicker function, add the following lines
var date = new Date();
Then within datepicker function, set maxDate to your variable, eg