how to set second date

i am using this code for from and to date select, when i select first date i want to set date in second picket get automatically set to 7 days after first one.

var input;
jQuery.noConflict()(function ($) {

var from_$input = $('#datefrom').pickadate({ min: true, max: false, today: '',
clear: 'clear',
close: 'Cancel',
format: 'dd/mm/yyyy',
selectYears: true,

selectMonths: true
}),

from_picker = from_$input.pickadate('picker')

var to_$input = $('#dateto').pickadate({ min: true, max: false, today: '',
clear: 'clear',
close: 'Cancel',
format: 'dd/mm/yyyy',
selectYears: true,
selectMonths: true
}),

to_picker = to_$input.pickadate('picker')

// Check if there's a “from” or “to” date to start with.

if (from_picker.get('value')) {

to_picker.set('min', from_picker.get('select'))

}

if (to_picker.get('value')) {

from_picker.set('max', to_picker.get('select'))

}

// When something is selected, update the “from” and “to” limits.

from_picker.on('set', function (event) {

if (event.select) {

to_picker.set('min', from_picker.get('select'))

}

else if ('clear' in event) {

to_picker.set('min', false)

}

})

to_picker.on('set', function (event) {

if (event.select) {

from_picker.set('max', to_picker.get('select'))

}

else if ('clear' in event) {

from_picker.set('max', false)

}

})

});