disable past dates on datepicker

Question

How to disable past dates from the current date on a datetimepicker? I tried few posts for similar question but was unable to achieve it, Below is what I tried

Answer 1

To disable all previous dates, give start date as today date

startDate: new Date()

Solution: disable all previous dates from today

$(function() {
    $( "#datepicker" ).datepicker({ startDate: new Date()});
 });

 Select Date 

Solution: disable all past dates from a particular date.

$(function() {
    $( "#datepicker" ).datepicker({ startDate: new Date("2019-10-15")});
});

 Select Date 

This will disable all days before the date 15th October 2019 (2019-10-15)