Hi @yarongo
The datepicker uses jquery UI datepicker and you can update the minDate and/or maxDate values like this:
//This is an example field key. You need to use your own
jQuery( '.acf-field-54cfe68700b24 .acf-date_picker input.input' ).datepicker( 'option', 'minDate', date.format() );
so if you target a change in the first datepicker, find out the value set and use it to set the minDate with the above code it should work. I’ve done something similar before myself 🙂